Combined Modality Intervention for ADHD With Comorbid Reading Disorders: A Proof of Concept Study

Abstract

To evaluate the relative efficacy of two reading programs with and without adjunctive stimulant medication for children with attention-deficit/hyperactivity disorder and comorbid reading disorder (ADHD+RD). Sixty-five children (7–11 years in age) were assigned randomly to one of three intensive remedial academic programs (phonologically or strategy-based reading instruction, or general academic strategy and social skills training) in combination with either immediate-release methylphenidate or placebo. Multiple-blind procedures were used for medication/placebo, given twice daily. Children received 35 hours of instruction in 10 weeks, taught by a trained teacher in a separate school classroom, in small matched groups of 2 to 3. Children’s behavior and reading abilities were assessed before and after intervention. Stimulant medication produced expected beneficial effects on hyperactive/impulsive behavioral symptoms (reported by classroom teachers) but none on reading. Children receiving a reading program showed greater gains than controls on multiple standardized measures of reading and related skills (regardless of medication status). Small sample sizes precluded interpretation of possible potentiating effects of stimulant medication on reading skills taught in particular reading programs. Intensive reading instruction, regardless of treatment with stimulant medication, may be efficacious in improving reading problems in children with ADHD+RD and warrants further investigation in a large-scale study.

Keywords

attention-deficit/hyperactivity disorder reading disorder dyslexia methylphenidate remediation

Attention-deficit/hyperactivity disorder (ADHD) and dyslexia (or reading disorder, RD) are both commonly occurring neurodevelopmental disorders, each conservatively estimated to affect about 5% of the general school-age population (Katusic, Colligan, Barbaresi, Schaid, & Jacobsen, 2001; Pastor & Reuben, 2008; Polanczyk & Rohde, 2007; Willcutt, 2012). ADHD and RD are found to co-occur more frequently than expected by chance in both clinical and epidemiological samples, with rates of overlap varying from 15% to 40% (Goldston et al., 2007; Sexton, Gelhorn, Bell, & Classi, 2012; Willcutt, Pennington, & DeFries, 2000). In fact, large-scale epidemiological work finds ADHD to be the most common concomitant of RD in childhood (Carroll, Maughan, Goodman, & Meltzer, 2005; Maughan & Carroll, 2006). Both disorders are highly heritable (Little, Hart, Schatschneider, & Taylor, 2014; Rosenberg, Pennington, Willcutt, & Olson, 2012; Willcutt, Pennington, Olson, & DeFries, 2007) and share specific cognitive weaknesses such as slow processing speed and/or poor orthographic processing (Cheung, Fazier-Wood, Asherson, Rijsdijk, & Kuntsi, 2014; McGrath et al., 2011; Miranda, Presentación, Siegenthaler, Colomer, & Pinto, 2011; Shanahan et al., 2006; Willcutt et al., 2010; Willcutt, Pennington, Olson, Chhabildas, & Hulslander, 2005). The comorbidity between ADHD (particularly the inattention dimension) and RD is due largely to genetic influences, both contemporaneously and longitudinally (Cornish, Savage, Hocking, & Hollis, 2011; Wadsworth, DeFries, Willcutt, Pennington, & Olson, 2015). Genetic modeling has shown not only that word decoding and reading comprehension largely share the same genetic etiology in elementary school children but also that the association with inattention is mostly explained by shared genetic influences (Plourde et al., 2015). Importantly, ADHD+RD (as well as both ADHD and RD alone) persist into adolescence and adulthood, with increased risk for educational, socioeconomical, and occupational problems through the lifespan (McGee, Prior, Williams, Smart, & Sanson, 2002; Rabiner & Coie, 2000; Yoshimasu et al., 2010). Thus, early identification and effective intervention are important.

Considerable advances have been made in developing effective intervention for each disorder separately, but surprisingly little research has directly evaluated intervention for children with co-occurring ADHD+RD (Miranda et al., 2011; Sexton et al., 2012). A logical starting point in developing a comprehensive treatment plan for ADHD+RD is to test a combination of the best known treatments for each of the disorders separately: specifically, stimulant medication to reduce the behavioral symptoms for ADHD and intense, focused reading instruction for RD. The effects of medication on the behavioral symptoms of ADHD and of reading instruction on reading outcomes in RD have been well documented, but the effectiveness of these interventions for comorbid ADHD+RD is unclear, as indicated in the review below.

Impact of Stimulant Medication on Behavior and Reading in ADHD+RD

There is robust evidence that stimulant medication, especially methylphenidate (MPH), produces immediate and clinically relevant beneficial effects on the core behavioral symptoms of children and adolescents with ADHD (i.e., inattentiveness, hyperactivity, impulsivity), particularly in the classroom as reported by teachers, without an increase in serious side effects, at least in the short term (for recent meta-analysis of randomized clinical trials, see Storebø et al., 2015). The magnitude of these effects is uncertain due to the low quality of available studies arising from high risks of bias and sample heterogeneity (Storebø et al., 2015). We could locate only one study that specifically compared the therapeutic response to stimulant medication in children with ADHD with and without comorbid specific learning disorder (SLD) in math or reading or both (Grizenko, Bhat, Schwartz, Ter-Stepanian, & Joober, 2006). Results of this randomized placebo-controlled crossover trial revealed that the clinical response to medication was significantly lower in those with comorbid SLD (55%) compared to those without comorbid SLD (75%), particularly in children with ADHD+SLD in mathematics (37%). The robustness of these findings awaits replication in a larger scale trial.

By contrast, evidence for beneficial effects of stimulant medication on reading in children with ADHD or ADHD+RD remains equivocal (for a review, see Baweja, Mattison, & Waxmonsky, 2015). While the evidence for beneficial effects of stimulant medication on school performance in youngsters with ADHD is quite strong, with the largest impact’s being on academic seatwork productivity and on-task performance, there is little evidence of meaningful improvements in reading skills per se (Baweja et al., 2015). For example, some large-scale retrospective population studies have shown more favorable long-term school outcomes for children with ADHD treated with stimulant medication compared to those untreated or nonadherent to medication: Benefits were found for rates of absenteeism, grade retention, grade point average, and mild improvements in reading and/or math achievement scores (Barbaresi, Katusic, Colligan, Weaver, & Jacobsen, 2007; Marcus & Durkin, 2011; MTA Cooperative Group, 2004; Powers, Marks, Miller, Newcorn, & Halperin, 2008; Scheffler et al., 2009). Also, Zoëga and colleagues (2012) reported that earlier treatment with stimulant medication reduces the decline in academic scores in mathematics and language arts with increasing age, especially for boys. However, none of these studies investigated stimulant effects on reading in youngsters with ADHD, although Scheffler and colleagues (2009) reported that the beneficial effect of medication was reduced in children with Individualized Education Programs, raising the possibility that stimulant medication may not benefit children with comorbid learning or reading difficulties to the same extent.

The few studies that have directly evaluated whether medication influences reading outcomes in children with comorbid ADHD+RD have focused on immediate, short-term (e.g., within a few hours of the medication administration) rather than long-term (daily treatment for a period of time) effects of MPH on reading proficiency. For example, in a double-blind, placebo-controlled crossover trial, Bental and Tirosh (2008) reported short-term benefits of MPH on reading skills (word and nonword reading, rapid naming of digits) in boys (7–12 years old) with comorbid ADHD+RD. Notably, this benefit was state dependent, such that children’s performance improved over baseline after receiving stimulant medication but did not carry over to improve performance in a subsequent placebo condition 1 week later. No effect of MPH was observed on other reading and reading-related skills, including spelling accuracy, phonological processing, or reading comprehension (see Note 1). Tannock, Martinussen, and Frijters (2000) also reported an acute beneficial effect of MPH on rapid automatized naming in English-speaking children with ADHD (ages 7–12 years, 25% of whom were identified as having ADHD+RD), using a double-blind, randomized, placebo-controlled, crossover trial. Finally, Williamson, Murray, Damaraju, Ascher, and Starr (2014) compared reading and math outcomes in children with ADHD with or without comorbid learning disabilities (LD) as a function of MPH. Children (ages 9–12) were tested on two separate days following random and double-blind assignment to MPH or placebo. Results showed that regardless of LD status, children with ADHD read text more fluently, wrote more legibly, and performed mathematical calculations more quickly without sacrificing accuracy when they received MPH compared to placebo. Reading comprehension was also higher after receiving MPH in those without LD (a trend found in those with LD). However, measures were not collected at the start of the study, so the extent to which MPH was associated with improved learning over time, as opposed to improved test-taking skills, is unknown. Together, these studies suggest that MPH may be associated with improved performance on some reading and reading-related tasks in children with ADHD+RD. However, it is unclear whether the short-term benefits associated with MPH may be translated into longer-term gains in reading performance.

To our knowledge, in the past 25 years, only one prospective longitudinal (i.e., pre-post) study has examined long-term effectiveness (i.e., beyond 1 month) of MPH use on reading performance in children diagnosed with both ADHD and RD (Keulers et al., 2007). This study found that while children with ADHD+RD (ages 6–13 years) who received MPH during a period of 3 to 16 months demonstrated improved word and nonword reading fluency (as measured by raw but not standard scores), these gains were only marginally greater than those of the children with RD who did not receive stimulant medication. These findings are limited, however, due to the use of an unblinded clinical trial. Moreover, both groups of children with RD received reading tutoring throughout the duration of the study, making it difficult to disentangle the positive effects of MPH from that of the tutoring.

Collectively, the extant research regarding the beneficial effects of stimulant medication on the behavior and reading abilities of children with ADHD+RD suggests that the medication does reduce the core behavioral symptoms of ADHD but possibly to a lesser extent than in children without comorbid RD. There is, however, little evidence for robust stimulant-related improvements in reading skills in youngsters with ADHD+RD. Moreover, any impact of stimulant medication on reading may be indirect via its beneficial effects on attention. This is because behavioral attention is a significant and unique predictor of word-reading proficiency (Dally, 2006; Gray, Carter, Briggs-Gowan, Jones, & Wagmiller, 2014; Martinussen, Grimbos, & Ferrari, 2014; Sáez, Folsom, Al Otaiba, & Schatschneider, 2012) and because inattentive behavior is associated with reduced ability to acquire emergent prereading skills and word-reading efficiency (Dittman, 2013; Sims & Lonigan, 2013) and stimulant medication is known to reduce inattentive behavior in the classroom (Storebø et al., 2015).

Effects of Reading Remediation on Reading and Behavior in ADHD+RD

For children with RD alone, substantial evidence from controlled reading remediation studies indicates beneficial effects of focused and systematic reading instruction (e.g., Blachman et al., 2004; Denton, 2012; Torgesen et al., 2001). In the United States, multitiered reading intervention is increasingly provided as a component of Response to Intervention (RtI), with small-group intensive daily instruction provided to youngsters with persisting difficulties and inadequate response to previous interventions (Berkeley, Bender, Peaster, & Saunders, 2009; Denton, 2012). Moreover, the RtI literature has sought to identify characteristics of nonresponders to the various tiers of intervention, but behavioral characteristics, such inattention or hyperactivity/impulsivity, are rarely considered (e.g., Lam & McMaster, 2014).

The current evidence indicates that programs with both intensive phonologically-based instruction and application of word-decoding strategies are most effective for children with RD (Lovett et al., 2008; Lovett, Lacerenza, Borden, et al., 2000; Morris et al., 2012). However, of concern is the evidence that the co-occurrence of marked inattentive and/or disruptive behavior with reading problems predicts a poor response to reading programs that otherwise have demonstrated effectiveness for children with RDs (Al Otaiba & Fuchs, 2002, 2006; Rabiner & Malone, 2004). In fact, Rabiner and Malone (2004) found that, while struggling kindergarten readers without concurrent attention difficulties experienced substantial gains in reading achievement following a year-long phonics-based reading intervention program, no discernible improvement was found for children who struggled with both reading and attention. By contrast, Roberts and colleagues (2014) found increasingly intensive reading instruction during a period of 3 years, based on the RtI framework, improved both reading and behavioral inattention in middle-school students, with reading intervention’s directly improving reading, which in turn had a positive impact on inattention. However, it remains unknown whether these findings would generalize to students with a clinical diagnosis of ADHD+RD.

It may be that, for children with comorbid ADHD+RD, the specific content or pedagogical strategies used in an intervention program need to be adapted to facilitate learning. For example, it may be that these children benefit more from a phonological rather than a decoding strategy focus, or vice versa. They may also require greater teacher support to highlight important material and increase on-task behavior, as well as use varied materials and activities to maintain engagement (Deault, Savage, & Abrami, 2009). Alter-natively, it may be that a combination of both stimulant medication treatment and targeted academic instruction is necessary to promote gains in both reading achievement and attention in these children. Finally, the type of reading intervention may interact differentially with stimulant medication treatment, suggesting the need for a component-based evaluation of treatment options, with medication crossed with different reading interventions.

Both stimulant medication and intensive targeted reading intervention are well-validated approaches for treating ADHD and RD, respectively; however, to date, no study has directly compared the effects of these best available approaches for treating elementary school–age children who struggle with both ADHD and RD. This is important because, while many school-age children with ADHD are often prescribed MPH or other stimulant medication to enhance their behavior and academic performance (LeFever, Dawson, & Morrow, 1999), the long-term effectiveness of MPH on learning and academic outcomes in those with ADHD+RD remains unclear (Currie, Stabile, & Jones, 2014). Thus, in the present study, we used a prospective, double-blind, randomized controlled trial of combined academic and pharmacological intervention for children with ADHD+RD to evaluate improvements in both behavioral and reading outcomes. The data for this study were collected some years ago (1996–2001); these data remain important to report because they allow us to address, for the first time, the following objectives:

Determine whether 4 months of MPH treatment in the absence of concurrent reading intervention is associated with improved behavioral and reading performance in children diagnosed with ADHD+RD. To do so, we compared pre and post behavioral and academic performance between those receiving MPH and those receiving placebo, collapsed across remediation program.

Evaluate the relative efficacy of two forms of specific reading instruction that are known to be effective for children with RD, compared to general academic strategy and social skills training, for improving the reading and behavioral difficulties of children with ADHD+RD in the absence of concurrent pharmacological treatment. Accordingly, we compared pre and post behavioral and academic performance across the three remediation groups, collapsed across medication status.

Explore whether adjunctive treatment with stimulant medication potentiates the effects of intense reading instruction for children with ADHD+RD and whether any potentiation differs across reading instructional emphasis (e.g., phonological or strategy based). To this end we conducted post hoc analyses comparing the effect of MPH versus placebo on academic outcomes within each remediation program.

To our knowledge, this is the first study to examine the efficacy of intensive reading remediation, with or without stimulant medication treatment, on improving reading and behavioral outcomes in children with comorbid ADHD+RD. As such, we consider it to be a proof-of-concept rather than an efficacy trial.

Method

Participants

A total of 65 children, ages 7 to 11 years, with a confirmed diagnosis of ADHD+RD participated. Most (> 85%) were recruited from schools and community medical clinics via mailings and presentations to school and medical personnel (e.g., teachers, principals, psychologists, pediatricians, family practitioners); the remainder were recruited directly from an outpatient neuropsychiatric clinic specializing in ADHD. Inclusion criteria were Diagnostic and Statistical Manual of Mental Disorders (fourth edition [DSM-IV]; American Psychiatric Association, 1994) diagnosis of ADHD and RD (based on clinical diagnostic assessment described below), age between 7 and 11 years, IQ greater than 80 (confirmed with the Wechsler Intelligence Scale for Children, third edition [WISC-III]; Wechsler, 1999), full-time attendance in a local school and consent for child to be withdrawn from class to participate in the intervention study, English as the primary language spoken by parent and child, and parental consent for the child to participate in the randomized controlled trial. Children attending full-time French immersion programs, those who had chronic medical or neurological conditions, and those with a history of head injury/loss of consciousness requiring hospitalization were excluded, as were children with a history of adverse or poor response to stimulant medication. Participants were primarily Caucasian (90%), with the remaining children being African American (4%), Hispanic (1%), or Asian (5%).

Screening and Diagnostic Procedure

Telephone interviews were conducted to ascertain the child’s eligibility for the study (age, reading problems reported by school, persistent symptoms of ADHD at home and school, English as primary language). Families who met these screening criteria were invited to attend a diagnostic clinic for a full clinical assessment. The assessment involved semistructured interviews conducted with parents (Parent Interview for Child Symptoms–IV; Ickowicz et al. 2006) and the participant’s classroom teacher (Teacher Telephone Interview–IV; Hum, 2004), by trained clinicians, and parent and teacher behavior ratings using Conners’ Rating Scales–Revised (CRS-R; Conners, 1997). Diagnosis of comorbid anxiety, oppositional disorders, or conduct disorders were based on the parent interview because the teacher interview provides only screening items for these disorders. Children completed standardized measures of intellectual ability (WISC-III; Wechsler, 1999), oral language (Clinical Evaluation of Language Fundamentals–III; Semel, Wiig, & Secord, 1995), and reading abilities (Reading subtest of the Wide Range Achievement Test–3 [WRAT-3]; Jastak & Wilkinson, 1984), and the Word Identification and Word Attack subtests of the Woodcock Reading Mastery Tests–Revised [WRMT-R]; Woodcock, 1987).

Final participant selection was based on the following inclusion criteria: (a) DSM-IV diagnosis of ADHD, based on the diagnostic instruments listed above, with evidence of symptoms causing impairment at school and home but not receiving any form of psychopharmacological treatment at the start of the study; (b) at least average intellectual ability, as measured by the WISC Full-Scale or Performance IQ score; and (c) a diagnosis of RD based on low achievement criteria, namely, a score of at least 1.5 standard deviations less than age-level expectations on at least two of the standardized reading tests or 1 standard deviation less than age-level expectation on three tests. The replication requirement was adopted to ensure that achievement deficits were not artifacts of differences in the word frequency or phonetic predictability distributions for different tests. Also, previous research has confirmed that identification of RD based on any single criterion has limited stability over time (e.g., Fletcher, Stuebing, Morris, & Lyon, 2013). Low achievement criteria were adopted for the definition of RD to allow inclusion of lower-IQ children with reading impairment, congruent with other recent intervention research on RD (Lovett, Lacerenza, Borden, et al., 2000; Morris et al., 2012) and based on longitudinal data showing no differences in rates of reading growth over time among children whose reading achievement was and was not discrepant from IQ (Francis, Shaywitz, Steubing, Shaywitz, & Fletcher, 1996). Cases were distributed across our two low-achievement criteria such that 57% qualified on both criteria, 40% qualified on the 1 standard deviation three-test criterion, and only two participants qualified on the 1.5 standard deviations on two-test criterion. All participants passed routine audiometric screening, and their diagnostic profiles were reviewed and confirmed by the clinical team psychiatrist. The flow of participants from initial contact, through screening, assessment, and randomization, is presented in Figure 1. Child and family characteristics are summarized in Table 1.

Figure 1.

Flow Chart Indicating the Flow of Participant From Initial Contact, Through Screening, Assessment, and Randomization.

Table 1.

Descriptive Characteristics of the Sample.

Characteristic/Test	Total sample(n = 65)	Methylphenidate			Placebo
Characteristic/Test	Total sample(n = 65)	PHAB(n = 17)	WIST(n = 10)	GCAST(n = 7)	PHAB(n = 11)	WIST(n = 13)	GCAST(n = 7)
Age (SD)	8.5 (1.4)	8.2 (1.2)	9.3 (2.1)	8.1 (1.1)	8.9 (1.0)	8.1 (1.4)	8.5 (1.0)
Males:Females	49:16	15:3	11:1	4:5	7:3	7:4	5:0
SES	6.4 (1.7)	6.8 (1.5)	6.0 (1.3)	6.5 (1.9)	5.7 (1.6)	6.9 (1.5)	6.9 (1.4)
WISC-III
Verbal IQ	91.1 (11.2)	94.9 (9.7)	93.8 (12.5)	84.2 (7.0)	84.9 (10.6)	94.8 (10.9)	94.6 (10.6)
Performance IQ	94.1 (13.2)	92.6 (13)	87.9 (13.8)	90.2 (9.2)	93.3 (15.3)	100.8 (12.2)	97.3 (10.3)
Full-scale IQ	91.5 (10.6)	92.9 (9.7)	90.1 (12.0)	85.8 (7.1)	87.1 (11.8)	97.2 (9.9)	95.4 (7.3)
CELF
Expressive	92.0 (16.0)	92.3 (11.6)	95.7 (16.0)	85 (11.2)	86.3 (20.4)	97.1 (14.6)	95.1 (13.5)
Receptive	87.0 (15.5)	87.9 (17.4)	90.6 (11.7)	79.8 (8.7)	80.2 (16.1)	89.9 (15.7)	94.6 (16.1)
ADHD symptoms^a
Parent	11.2 (3.5)	11.6 (1.3)	9.7 (3.8)	8.8 (3.6)	11.1 (4.1)	12.7 (2.7)	12.6 (3.5)
Teacher	10.2 (2.9)	9.9 (3.1)	11.4 (2.5)	9.6 (1.1)	9.3 (3.6)	11.5 (1.9)	9.7 (3.2)
Comorbidity (%)^b
ODD	29.3	13.3	30.0	33.3	44.4	40.0	20.0
CD	8.6	0.0	30.0	11.1	0.0	0.0	20.0

Note. PHAB = Phonological Analysis and Blending; WIST = Word Identification and Strategy Training; GCAST = General Cognitive and Academic Strategy Training; SES = Socioeconomic status (defined as the maximum level of parental education on a 9-point scale; 1 = no schooling to 9 = completed university degree; most parents had completed some high school to some community college); WISC-III = Wechsler Intelligence Scale for Children, third edition; CELF = Clinical Evaluation of Language Fundamentals; ADHD = attention-deficit/hyperactivity disorder; ODD = oppositional defiant disorder; CD = conduct disorder.

Based on children for whom valid Conners’ Rating Scales questionnaires were obtained. ^bBased on either parent or teacher interview. No differences between remediation and medication groups were observed on any of these measures.

Study Design

A randomized, controlled, full factorial (3 × 2) design was used to evaluate the relative efficacy of three remedial treatment programs in combination with either the stimulant medication MPH or placebo. Two of the selected programs have demonstrated efficacy for improved reading skills in children with RD (Lovett et al., 1994; Lovett, Lacerenza, & Borden, 2000; Lovett, Lacerenza, Borden, et al., 2000); the third program was developed specifically for this study to serve as an active control treatment. The medication procedure and remediation programs are described in more detail below. Pre- and postintervention assessments were conducted in a classroom laboratory in a clinical setting (i.e., not in the school classroom) by testers who were blind to the study objectives and treatment conditions.

Medication Procedures

Following the baseline assessment and randomization, each participant completed a 2- to 3-week titration phase in which the dose of MPH or placebo was increased in 5-milligram steps to a maximum oral dose of 0.7 milligram/kilogram twice daily or 20 milligrams twice daily, whichever was achieved first. Identical, scored 10-milligram pills of MPH and placebo was used. Throughout the study, behavioral changes and side effects were monitored closely by the research team and the study’s psychiatrist (the fifth author) using the Side Effects Rating Scale (Barkley, 1990) and the Iowa-Conners Scale (Loney & Milich, 1982), which were administered by means of weekly telephone calls to parents and teacher. Each family met with the research team psychiatrist at the end of the titration phase to review the treatment response and determine the dosage to be used during the academic intervention trial. Parents were then provided with a 4-month supply of pills, each month packaged separately. The MPH and placebo pills were identical in color, shape, and size and were administered in a double-blind manner twice daily (once in the morning before school and once at lunch; see Note 2). Research staff recorded the number of pills returned at study completion to estimate treatment compliance, which was high (average of about 90%).

Remedial Treatment Programs

Children were randomly assigned to receive one of three remedial treatment programs; each consisted of 35 one-hour sessions administered four times a week for about 10 weeks at one of two public schools. Previous studies have shown that 35 hours of intensive instruction can lead to improved reading outcomes for children who struggle with reading (Lovett et al., 1994; Lovett, Lacerenza, Borden, 2000). Children were brought from their nearby home schools to one of the two schools by taxi or school bus. They were taught in small groups of 2 to 3 students, matched for age and word identification skill, in a separate room away from their regular class. The programs were all taught by an experienced certified teacher who had been trained in the implementation of all three remediation programs and in classroom management techniques for ADHD. All of the children and all three programs were taught by the same interventionist (the third author), with the exception of 8 children (12% of the sample), who had been randomly assigned to one of the two reading programs: Phonological Analysis and Blending/Direct Instruction (PHAB/DI, n = 5) or Word Identification and Strategy Training (WIST, n = 3) and were taught by a trained replacement teacher when the primary interventionist was ill.

The two reading programs (PHAB/DI and WIST), which were developed and validated by Lovett and colleagues for use with children with RD (Lovett et al., 1994; Lovett, Lacerenza, Borden, 2000), offered intensive instruction in decoding words and reading text (see Note 3). PHAB/DI used lessons from the Reading Mastery I/II Fast Cycle and the Corrective Reading programs (Engelmann & Bruner, 1988; Engelmann, Carnine, & Johnson, 1988; Engelmann, Johnson, et al., 1988), which train phonological analysis, phonological blending, and letter-sound association skills in the context of word recognition and decoding instruction. In contrast, WIST trains children to use and monitor the application of four metacognitive decoding strategies (word identification by analogy, seeking the part of the word you already know, attempting variable vowel pronunciations, peeling off prefixes and suffixes). The first WIST strategy and the Keywords are based on the Benchmark School Word Identification/Vocabulary Development Program (Gaskins, Downer, & Gaskins, 1986). The PHAB/DI and WIST programs drew from an identical corpus of words during instruction, the majority of which exemplified regular spelling-to-sound correspondences.

The third program, General Cognitive and Academic Strategy Training (GCAST), which was developed specifically for this study, trained children to use and monitor the application of a set of metacognitive strategies for both academic (mathematics, organizational skills, and reasoning, but not reading) and social settings. This program did not teach or require reading skills; written material was kept to a minimum and was read to the children.

Treatment manuals can be obtained from the authors (seventh author for reading programs; third author for GCAST). All three programs included modifications to better fit the information-processing problems of children with ADHD+RD (e.g., slow processing, poor working memory and sustained attention) and facilitate active engagement. These included explicit instruction, oral and visual prompts, frequent practice and review, massed practice and routinization, reduction of task complexity and of working memory demands, chunking and repetition of instructions with pausing, frequent change of response modality, increased opportunities to respond, and frequent task redirects and feedback (see http://www.teachadhd.ca for rationale and examples).

The children’s previous literacy instruction was variable, as none of the children’s home schools used an official core reading program centrally endorsed by the school board. Instead, teachers followed the Provincial Curriculum Guidelines for teaching language (reading, writing, oral language skills) in use at that time (Ontario Ministry of Education and Training, 1997). In contrast to PHAB/DI and WIST, the provincial literacy curriculum did not emphasize explicit instruction in phonological or metacognitive decoding strategies. Thus, children assigned to the two reading programs under investigation were taught novel strategies for decoding words. The inclusion of the PHAB/DI, WIST, and GCAST programs in the current study allows us to investigate for the first time the impact of receiving an explicit and intensive reading program (i.e., PHAB/DI and WIST vs. GCAST) as well as effects that may be specific to a particular program (i.e., PHAB/DI vs. WIST) for children with ADHD+RD.

Treatment Outcome Measures

Primary outcomes

Two primary outcome measures were specified (one pertaining to ADHD and the other to reading): namely, ADHD symptoms and single-word reading. Core symptoms of ADHD were assessed using the inattention and hyperactivity/impulsivity subscales from parent and teacher versions of the CRS-R (Conners, 1997). Single word reading was assessed using the Word Attack and Word Identification subtests from the WRMT-R.

Secondary program-specific outcomes

Two additional measures were included to test predicted program-specific effects; the Goldman-Fristoe-Woodcock Sound Analysis subtest (Goldman, Fristoe, & Woodcock, 1974) was used to measure phonological analysis skills predicted to be most improved by PHAB/DI; and the Keyword Test was used to measure word decoding, predicted to be most improved by WIST.

Tertiary transfer-of-training/generalization measures

Treatment effects on co-occurring oppositional behavior were assessed using the Oppositional Behavior subscale of the Parent and Teacher CRS-R. Word decoding skills were assessed using the Test of Transfer, which includes 371 untrained words that vary in systematic ways from the 120 keyword spelling patterns used in training (e.g., the keyword bake is represented by the transfer probes fake, babe, bike, baker). Testing stops after 40 consecutive errors (Lovett et al., 1994). Also, children’s progress in two other academic domains was evaluated (one reading, one nonreading): Reading comprehension was evaluated with the WRMT-R Passage Comprehension test, and arithmetic computation skills were evaluated with the Arithmetic subtest of the Wide Range Achievement Test–Revised (WRAT-R).

Compliance With Assigned Intervention Protocols

All children completed the required 35 hours of instruction in their randomly assigned instructional condition (100% compliance), but within the initial 2-week dose-adjustment phase and prior to starting the academic programs, 20% of parents (n = 13) requested a change in their child’s assigned medication condition (8 from placebo to MPH; 5 from MPH to placebo). These changes, plus recruitment difficulties and the need to draw on a substitute interventionist, led to some unevenness in the number of children per condition. Despite this unevenness, no significant differences were observed across the two medication and three academic programs on any of the variables in Table 1, providing evidence that random assignment was successful.

One of the 13 families requesting a change in the child’s medication assignment also requested to be informed as to the child’s original medication condition prior to changing medication conditions, but the remaining 12 did not and so remained blind to both the original and second medication condition until study completion. There were no other changes in assigned conditions (medication, program) once the academic instructional programs had commenced. Thus, we decided to proceed with the planned intent-to-treat (ITT) analyses, which are reported below. Given that the ITT analyses included data from the 13 children who had changed their original randomized assignment to medication condition (8 from placebo to MPH; 5 from MPH to placebo) prior to commencing the reading programs, we reran the analysis using an as-treated approach, since the ITT approach may underestimate main effects of medication effects or its interaction with the academic programs. We report only substantial changes in findings using the as-treated approach (see the Supplemental Analysis section). However, we acknowledge that neither approach adequately addresses the potential threat to the study’s internal validity, given the small sample sizes together with attrition from the assigned medication condition.

Data Analysis

The effects of reading program and stimulant medication on both reading and behavioral outcomes were evaluated via focused contrasts. In each case, an analysis of covariance (ANCOVA) was run on posttest scores using pretest scores as a covariate. In lieu of testing and interpreting the omnibus effects of the reading program main effects, specific planned a priori contrasts were estimated, which compared the adjusted posttest mean scores for the three reading groups. Advocates of planned contrasts argue that a priori contrasts are more powerful and ask more focused questions of treatment outcome data (Abdi, Edelman, Valentin, & Dowling, 2009; Olejnik & Hess, 1997; Rosnow & Rosenthal, 2002). When theoretical or clinical reasons exist to suppose a particular pattern to research results, a priori contrasts also yield a readily interpretable effect size, r. Note that the magnitude of this effect size reported in the text and tables below should be interpreted as a correlation coefficient, with moderate effects being those around r = .25 and so forth.

When program-related measures involved larger subsyllabic units or whole words, WIST was expected to outperform PHAB/DI. In contrast, when program-related measures involved smaller subsyllabic units, PHAB/DI was expected to produce larger gains. Thus, the PHAB/DI and WIST programs together were first contrasted with the GCAST program to determine differences in reading outcomes that were due to the active reading treatments. PHAB/DI and WIST were then contrasted with each other to capture effects specific to these two interventions.

Each ANCOVA model was thoroughly evaluated against the assumptions of homoscedasticity, homogeneity of regression slopes, linearity, and conditional normality. The first three assumptions were taken very seriously because their failure would dramatically increase Type I error rates in the current design of unequal group sizes (i.e., the Program × Medication models; Keselman & Keselman, 1988). In every case but one, all assumptions were met. The Keyword Test demonstrated marginally significant nonparallel regression slopes for both Reading Program (p = .08) and Medication (p = .09); thus the effects for this one outcome should be interpreted with caution. All behavioral outcome variables met all assumptions described previously. Significance levels for focused contrasts were calculated using the number of children involved in the specific contrast minus the number of groups involved in the contrast, not based on the overall degrees of freedom (Rosnow, Rosenthal, & Rubin 2000). Effect sizes for contrasts were also generated based on formulas provided by Rosnow et al. (2000). Our third research question was addressed by post hoc simple main effects analysis, comparing MPH and placebo outcome per reading program, with Bonferonni corrections.

Results

Behavioral Outcomes

Complete pretest and posttest data for both parent and teacher rating scales were available for 49 of the 65 participants, with 15 teacher ratings and 1 parent rating not completed. We analyzed behavioral data when both parent and teacher reports were present to ensure that results from these two sources could be compared. No significant differences between the analyzed sample and those excluded from the behavioral analyses were observed on any of the demographics or initial characteristics displayed in Table 1; however, because of the missing data, too few cases remained to evaluate full models evaluating the medication by program interaction. Rather, separate ANCOVAs evaluated the posttest behavioral indices of children in the MPH versus placebo treatment conditions (collapsed across academic programs) and then across the three academic programs (collapsed across medication status).

As shown in Table 2, a significant medication effect was seen for one of the primary behavioral outcome measures of ADHD: the teacher-rated DSM Hyperactive-Impulsive subscale of the CRS-R: F(1, 36) = 4.72, p = .04, r = .34, but not for the Inattentive subscale (p > .10, r = .22), albeit the latter showed a small to moderate effect size. A medication effect was also observed for the tertiary outcome measure of oppositional behavior on CRS-R, as rated by parents, F(1, 46) = 5.02, p = .03, r = .31.

Table 2.

Unadjusted Pre- and Posttest Means (and Standard Deviations) on Behavioral Measures by Medication Status.

CRS-R subtest^a	Pretest		Posttest		Adjusted posttest	PlaceboM (SE)	p	r _effect
CRS-R subtest^a	MPH(n = 23)	Placebo(n = 26)	MPH(n = 23)	Placebo(n = 26)	MPHM (SE)	PlaceboM (SE)	p	r _effect
Parent DSM Hyp-imp	69.3 (12.1)	68.6 (14.5)	63.4 (12.5)	65.9 (13.1)	63.2 (2.1)	66.1 (2.0)	.32	.15
Parent DSM inattentive	69.3 (11.2)	69.7 (9.0)	62.9 (10.6)	64.1 (10.8)	63.0 (2.0)	64.0 (1.9)	.70	.05
Parent oppositional	61.5 (10.5)	60.2 (11.8)	56.3 (11.6)	60.0 (12.3)	55.7 (1.6)	60.5 (1.5)	.03	.31
Teacher DSM Hyp-imp	70.2 (11.7)	69.7 (13.3)	62.0 (13.6)	67.9 (13.6)	59.6 (3.1)	68.7 (2.7)	.04	.34
Teacher DSM inattentive	68.8 (8.5)	72.9 (7.8)	62.6 (9.4)	67.2 (9.3)	62.6 (2.3)	66.8 (2.0)	.18	.22
Teacher oppositional	57.5 (10.4)	62.1 (15.6)	59.0 (15.8)	58.1 (13.6)	57.3 (3.2)	58.0 (2.8)	.86	.03

Note. CRS-R = Conners’ Rating Scales–Revised; DSM = Diagnostic and Statistical Manual of Mental Disorders; MPH = methylphenidate; Hyp-imp = hyperactivity and impulsivity.

All scores are T scores (M = 50; SD = 10); higher scores indicate more symptoms relative to children of similar age.

To evaluate the effect of remediation programs on behavior (collapsed across medication condition), ANCOVA models for teacher and parent ratings were conducted (see Tables 3 and 4). The a priori single degree of freedom contrasts revealed behavioral improvements following academic intervention as rated by parents on the CRS-R but not as rated by teachers. Specifically, parents of children in the PHAB/DI program reported greater reduction in hyperactive-impulsive symptoms than those in the WIST program, t(35) = 2.44, p = .02, r = .38. Also, parents (but not teachers) of children in the GCAST program reported greater improvements in inattentive symptoms compared to children receiving the reading programs, t(47) = 2.60, p < .01, r = .35. Inspection of the means and standard deviations for the posttest measures in Tables 2 and 4 indicated that medication improved but did not normalize the behavioral symptoms.

Table 3.

Raw Pre- and Posttest Means (and Standard Deviations) on Behavioral Measures by Reading Program Assignment.

CRS-R subtest	Pretest			Posttest
CRS-R subtest	PHAB/DI(n = 20)	WIST(n = 17)	GCAST(n = 12)	PHAB/DI(n = 20)	WIST(n = 17)	GCAST(n = 12)
Parent DSM Hyp-imp	68.3 (11.0)	71.5 (14.8)	66.3 (14.9)	61.5 (9.4)	71.2 (13.8)	61.1 (13.6)
Parent DSM inattentive	68.1 (9.7)	68.9 (10.7)	72.5 (9.8)	63.6 (10.3)	66.4 (7.4)	59.4 (14.0)
Parent oppositional	58.2 (6.8)	62.7 (14.6)	62.7 (11.2)	55.1 (8.7)	62.3 (15.2)	57.8 (10.7)
Teacher DSM Hyp-imp	68.3 (10.4)	73.5 (13.9)	69.4 (13.6)	61.1 (11.9)	67.1 (14.5)	67.2 (12.3)
Teacher DSM inattentive	69.0 (9.3)	72.5 (7.8)	71.9 (10.1)	62.5 (11.4)	66.4 (8.4)	68.3 (7.3)
Teacher oppositional	58.3 (12.0)	61.0 (14.6)	62.2 (16.6)	56.0 (12.1)	56.5 (15.1)	63.7 (12.5)

Note. CRS-R = Conners’ Rating Scales–Revised; PHAB/DI = Phonological Analysis and Blending/Direct Instruction; WIST = Word Identification Strategy Training; GCAST = General Cognitive and Academic Strategy Training; DSM = Diagnostic and Statistical Manual of Mental Disorders; Hyp-imp = hyperactivity and impulsivity.

Table 4.

Adjusted Posttest Means (and Standard Errors) of Behavioral Measures by Reading Program.

CRS-R	Adjusted posttest scores			PHAB/DI vs. WIST			Reading programs vs. GCAST
CRS-R	PHAB/DI	WIST	GCAST	Contrast	p	r _effect	Contrast	p	r _effect
Parent DSM Hyp-imp	61.9 (2.1)	69.7 (2.3)	62.6 (2.8)	7.8 (3.2)	.02	.38	3.2 (3.2)	.32	.14
Parent DSM inattentive	64.3 (2.0)	66.7 (2.2)	57.7 (2.6)	2.4 (2.9)	.42	.14	7.8 (3.0)	.01	.35
Parent oppositional	57.3 (1.8)	60.8 (1.9)	56.3 (2.2)	3.5 (2.6)	.18	.22	2.8 (2.6)	.29	.15
Teacher DSM Hyp-imp	61.7 (3.3)	67.2 (3.7)	66.8 (4.8)	5.5 (5.0)	.28	.18	2.3 (5.4)	.67	.06
Teacher DSM inattentive	62.6 (2.3)	66.0 (2.6)	68.2 (3.3)	3.4 (3.5)	.33	.16	3.9 (3.7)	.30	.15
Teacher oppositional	57.5 (3.2)	55.0 (3.5)	62.8 (4.6)	2.6 (4.7)	.59	.09	6.5 (5.2)	.22	.18

Note. CRS-R = Conners’ Rating Scales–Revised; PHAB/DI = Phonological Analysis and Blending/Direct Instruction; WIST = Word Identification and Strategy Training; GCAST = General Cognitive and Academic Strategy Training; DSM = Diagnostic and Statistical Manual of Mental Disorders; Hyp-imp = hyperactivity and impulsivity.

Academic Outcomes

Analyses of academic outcomes were conducted on the full sample of 65 children. A series of medication condition by reading program ANCOVAs were conducted to evaluate posttest scores on the primary, secondary, and tertiary measures of academic achievement using pretest scores as a covariate. As described above, omnibus F tests of significance are not reported in favor of the a priori focused contrasts comparing reading programs. The interaction between medication status and reading program was evaluated by means of post hoc simple main effect comparisons of MPH versus stimulant medication within each remediation group: We caution the reader that the small sample size in these groups precludes firm conclusions about any potentiating effects of medication on the academic outcomes.

The main effect of medication on academic outcomes, collapsing across reading programs, was also evaluated within ANCOVA models. As detailed in Table 5 (see Total MPH and Total Placebo columns and note c), no advantage was seen for MPH-treated participants for measures of single-word identification (i.e., WRMT-R Word Attack, WRMT-R Word Identification, Keywords, or Test of Transfer) and comprehension (i.e., WRMT-R Passage Comprehension). A significant beneficial main effect of MPH was observed for two outcomes: Goldman Fristoe Woodcock (GFW) Sound Analysis, F(1, 58) = 7.17, p = .003; and WRAT-R Arithmetic, F(1, 55) = 7.79, p = .01; however, as described later, these main effects may have been due in part to MPH-placebo differences within specific programs.

Table 5.

Adjusted Posttest Means (and Standard Errors) of Academic Outcomes by Reading Program and Medication Condition.

Reading measure	MPH				Placebo
Reading measure	PHAB/DI(n = 17)	WIST(n = 10)	GCAST(n = 7)	TotalMPH	PHAB/DI(n = 11)	WIST(n = 13)	GCAST(n = 7)	Totalplacebo
Primary measure
WRMT-R Word Attack^{a,b,c(marginal)}	81.4 (2.1)	81.6 (2.7)	77.4 (3.3)	80.1 (1.6)	75.2 (2.6)	80.3 (2.4)	73.1 (3.2)	76.2 (1.6)
WRMT-R Word Identification^b(marginal)	79.8 (1.1)	77.4 (1.5)	76.4 (1.8)	77.9 (0.9)	76.7 (1.4)	76.5 (1.3)	77.9 (1.8)	77.0 (0.9)
Secondary measure
Keywords^a,d	78.0 (3.0)	88.3 (3.9)	68.8 (4.7)	78.4 (2.3)	78.5 (3.7)	86.2 (3.4)	68.8 (4.7)	77.8 (2.3)
GFW Sound Analysis^c,e,f	45.3 (1.5)	42.7 (1.9)	41.6 (2.3)	43.2 (1.1)	42.2 (1.9)	37.1 (1.7)	37.8 (2.3)	39.1 (1.1)
Tertiary measure
Test of Transfer^a	40.8 (3.6)	44.1 (4.6)	29.3 (5.6)	38.1 (2.7)	37.4 (4.4)	40.3 (4.0)	31.5 (5.5)	36.4 (2.7)
WRMT-R Passage Comprehension^a	83.2 (1.6)	79.1 (2.0)	76.6 (2.5)	79.6 (1.2)	80.2 (1.9)	78.5 (1.8)	74.5 (2.4)	77.7 (1.2)
WRAT-R Arithmetic^c,f,g	83.4 (1.9)	89.3 (2.4)	91.6 (2.8)	88.1 (1.4)	85.7 (2.3)	82.2 (2.3)	79.9 (2.8)	82.6 (1.4)

Note. MPH = methylphenidate; PHAB/DI = Phonological Analysis and Blending/Direct Instruction; WIST = Word Identification and Strategy Training; GCAST = General Cognitive and Academic Strategy Training; WRMT-R = Woodcock Reading Mastery Tests–Revised; GFW = Goldman Fristoe Woodcock; WRAT-R = Wide Range Achievement Test–Revised.

Reading program > no reading program. ^bFor those in PHAB/DI, MPH > placebo. ^cMPH > placebo. ^dWIST > PHAB/DI. ^ePHAB/DI > WIST. ^fFor those in WIST, MPH > placebo. ^gFor those in GCAST, MPH > placebo.

The main effects of academic program on reading measures are shown in Tables 5 and 6. Children with ADHD+RD receiving a reading program showed greater gains on one of the two primary reading outcome measures (WRMT-R Word Attack, p = .05, r = .23), one of the secondary (trained knowledge) measures (Keywords, p < .01, r = .43), and two of the tertiary (generalization of training) measures (WRMT-R Passage Comprehension, p = .02, r = .28; Test of Transfer, p = .02, r = .28), compared to children in the GCAST program.

Table 6.

Raw Pre- and Posttest Means (and Standard Deviations) on Academic Achievement Measures by Reading Program and Medication Status.

Reading measure	MPH			Placebo
Reading measure	PHAB/DI(n = 17)	WIST(n = 10)	GCAST(n = 7)	PHAB/DI(n = 11)	WIST(n = 13)	GCAST(n = 7)
Pretest
Primary measure
WRMT-R Word Attack	70.1 (18.2)	77.1 (8.0)	81.4 (5.0)	70.1 (10.4)	79.8 (9.1)	75.7 (10.0)
WRMT-R Word Identification	73.5 (12.9)	75.6 (9.6)	80.0 (7.5)	71.7 (11.8)	76.2 (12.0)	75.4 (12.8)
Secondary measure
Keywords	50.2 (34.3)	66.5 (41.5)	74.9 (41.4)	64.4 (34.5)	55.3 (37.8)	48.9 (39.0)
GFW Sound Analysis	37.8 (10.6)	39.5 (10.4)	35.6 (10.9)	31.6 (10.8)	42.8 (12.9)	36.3 (7.7)
Tertiary measure
Test of Transfer	14.6 (21.4)	31.7 (33.9)	41.9 (33.6)	22.7 (27.7)	26.6 (35.3)	15.0 (25.6)
WRMT-R Passage Comprehension	68.1 (15.9)	77.2 (7.8)	83.7 (9.9)	71.1 (11.8)	77.7 (12.2)	78.9 (13.6)
WRAT-R Arithmetic	86.7 (11.5)	79.9 (8.0)	84.1 (12.2)	80.5 (9.1)	85.5 (15.9)	86.7 (12.6)
Posttest
Primary measure
WRMT-R Word Attack	78.6 (14.3)	82.8 (10.7)	81.1 (8.1)	72.5 (7.6)	83.2 (11.1)	73.6 (7.6)
WRMT-R Word Identification	78.5 (12.4)	78.0 (10.5)	81.0 (7.3)	73.7 (12.1)	77.6 (12.8)	78.3 (10.5)
Secondary measure
Keywords	71.5 (26.7)	94.4 (27.7)	81.4 (39.9)	83.0 (27.2)	83.6 (34.1)	61.1 (40.4)
GFW Sound Analysis	45.4 (9.6)	43.9 (5.8)	40.3 (12.7)	38.5 (8.9)	40.3 (9.6)	37.0 (5.9)
Tertiary measure
Test of Transfer	31.2 (27.7)	52.0 (40.2)	47.6 (36.9)	36.1 (28.3)	43.0 (36.7)	22.3 (31.8)
WRMT-R Passage Comprehension	77.3 (13.6)	80.9 (10.7)	84.6 (11.8)	76.9 (9.1)	80.7 (12.5)	76.3 (18.7)
WRAT-R Arithmetic	85.6 (8.8)	86.3 (13.4)	91.6 (11.0)	83.1 (7.7)	81.4 (13.2)	81.7 (13.8)

Primary effects of the academic programs on reading were seen for the Word Attack subtest (but not for Word Identification), with children receiving one of the reading programs scoring higher at posttest compared to those in the GCAST program (p = .05, r = .23). Specific reading program effects on the secondary outcome measures were seen for the Keyword test, with children in the WIST program gaining significantly more Keywords by posttest (p = .01, r = .44) compared to those in PHAB/DI, as predicted. Also, both reading programs accorded greater gains in Keyword scores at posttest (p = .01, r = .43) compared to GCAST. Also consistent with predictions, children in the PHAB/DI program showed more gains in phonological skills as indexed by their gains on the GFW Sound Analysis test (p = .04, r = .29). Significant effects of the reading programs compared to GCAST were also observed for the Test of Transfer (p = .02, r = .28) and for the WRMT Passage Comprehension subtest (p = .02, r = .28). Thus, collapsing across medication status, both reading programs had strong effects on reading outcomes (r_effect = .23 to .43).

The main effects of reading programs must be interpreted in light of MPH-placebo differences that varied across reading program. Post hoc comparisons of MPH and placebo for each of the three reading programs were conducted with a modified Bonferroni correction to control for experimentwise inflation of Type I error. The Bonferroni correction was chosen over the Benjamini-Hochberg false-discovery rate controlling procedure that is preferred by some because the number of post hoc comparisons was small and Bonferroni suffers no loss of statistical power while effectively controlling error rates under these conditions (Benjamini & Hochberg, 1995).

For children in the WIST program only, a large advantage on GFW Sound Analysis was observed for those assigned to the MPH condition versus placebo (M_diff = 5.7, SE = 2.6, p = .03, r = .46). In addition, a moderate (though marginally significant) advantage of MPH was observed for children in the PHAB/DI program only on the Word Attack (M_diff = 6.2, SE = 3.3, p = .06, r = .36) and Word Identification (M_diff = 3.2, SE = 1.8, p = .08, r = .29) outcomes. When the outcome was WRAT-R Arithmetic, a significant and substantial MPH advantage over placebo was observed for children in both the GCAST (M_diff = 11.7, SE = 4.0, p = .01, r = .47) and WIST (M_diff = 7.2, SE = 3.3, p = .03, r = .35) programs.

Supplemental Analysis (As Treated)

The reanalysis of the data using an as-treated approach yielded a similar pattern of findings overall but with a few differences: Medication had positive effects on teacher-rated inattention, F(1, 43) = 6.63, p = .01, as well as hyperactivity/impulsivity, F(1, 43) = 6.74, p = .01, but there were no medication effects on parent-rated ADHD symptoms or oppositional behavior. Since reading program assignment did not change, unlike medication status, the same pattern of outcomes was observed in the as-treated approach. The increased medication benefit versus placebo within reading-specific programs was demonstrated on different academic outcomes compared to the ITT analysis; however, the pattern was largely the same, with MPH plus academic intervention showing increased benefit for reading if the intervention was PHAB or WIST and increased benefit for arithmetic if the intervention was GCAST. The differences for these interaction effects are most likely attributable to instability due to the small sample sizes across the six cells of the design.

Discussion

This study represents the first controlled, double-blind, randomized treatment outcome study designed to investigate ways to address the dual needs of students with ADHD+RD: to reduce behavioral symptoms and improve reading abilities. Prior work with this population has focused primarily on the effectiveness of either stimulant medication (Bental & Tirosh, 2008; Keulers et al., 2007; Tannock et al., 2000; Williamson et al., 2014) or reading remediation (Rabiner & Malone, 2004; Roberts et al., 2014) on children’s behavior, attention, and reading-related difficulties. In the present controlled proof-of-concept study, we examined the relative efficacy of two different reading programs with and without adjunctive stimulant medication on improving both behavioral and reading skill outcomes in children with comborbid ADHD+RD.

Overall, our main findings show that (a) stimulant medication is effective in improving (but not normalizing) some behavioral symptoms of ADHD in children with ADHD+RD, but it was not effective as a stand-alone treatment in improving reading ability in the absence of concurrent reading remediation; and (b) intense reading remediation (in programs that emphasize phonological or word identification/strategy training) had substantial beneficial effects on reading abilities in children with comorbid ADHD+RD, but scores were not normalized. Also, we found that intense academic instruction also improved ADHD symptoms to some extent, as reported by parents, regardless of medication treatment. We discuss these finding in more detail below by describing the effects of MPH and reading remediation first on behavioral and then on academic outcomes.

Behavioral Outcomes

The behavioral outcomes associated with active stimulant treatment were generally consistent with prior research that finds robust evidence for beneficial effects on behavioral symptoms, particularly as reported by teachers (see meta-analyses by Prasad et al., 2013; Storebø et al., 2015). Specifically, we found that twice-daily immediate release MPH resulted in significant improvements in children’s behavioral core ADHD symptoms in the classroom (particularly hyperactivity/impulsivity, which is so noticeable in a classroom setting) as rated by their regular classroom teachers. Since these classroom teachers were kept uninformed as to the children’s assignment to medication condition, to minimize informant bias, we interpret this finding as evidence of a robust effect of medication on children’s classroom behavior, regardless of what academic program they received. It is not surprising that parents did not report improvements in their children’s behavioral symptoms of ADHD in the home setting, because the effects of each dose of this formulation would have lasted only 3 to 4 hours postingestion and so would have worn off by the time the children reached home at the end of the school day. However, parents did report medication-related improvements in oppositional behavior at home. So how are we to explain this finding? Oppositional symptoms include emotional symptoms (e.g., anger, irritability), as well as argumentative or defiant behavior and vindictiveness. Perhaps the behavioral and academic improvements in the classroom led to less frustration and upset in the children during the day so they returned home in a less emotional state.

Notably, we found positive effects of the academic programs on children’s behavior, as reported by parents, and regardless of the children’s medication status. Specifically, parents of children receiving the general strategy training (GCAST) reported an improvement in inattention compared to those receiving the reading programs, and parents of children receiving PHAB/DI reported significant improvements in their children’s hyperactive/impulsive behavior at home, compared to WIST. However, inspection of the summary data in Table 3 suggests that in fact parents of children in either the PHAB/DI or GCAST programs reported improved behavior at home, but parents of children in the WIST group did not, although our analytic approach did not provide a direct comparison among the three programs. However, it is interesting to note that parents’ ratings of their children’s ADHD symptoms improved as a function of instructional context, while teachers’ ratings improved as a function of medication status. This may reflect the fact that teachers could observe the direct effect of medication on behavior, while parents could not. Our finding that intensive academic instruction had positive effects on children’s behavior is consistent with the findings by Roberts et al. (2014), who reported that intensive reading remediation for a school sample of young adolescents with concurrent difficulties in attention and reading improved both behavioral and reading outcomes. Statistical modeling led these researchers to conclude that the intervention had direct effects on reading, which in turn improved attention, but that intervention had no direct effects on attention (Roberts et al., 2014). Our sample size is too small for statistical modeling and so precludes any interpretation of direct or indirect effects of academic intervention on behavior, which should be a focus of future research. Nonetheless, our findings suggest that intensive academic remediation may also contribute to improved behavior in elementary school–aged children with a clinical diagnosis of ADHD+RD.

Academic Outcomes

The beneficial effects of MPH on the children’s behavior at school did not transfer to academic skills. There was no significant main effect of medication status on any measures of single-word reading (WRMT-R Word Attack, WRMT-R Word Identification, Keywords or Test of Transfer) or reading comprehension (WRMT-R Passage Comprehension) at posttest, suggesting that medication alone is not sufficient to improve these measures of word-level decoding and passage comprehension skills over time in children with ADHD+RD. Of the secondary and tertiary measures that showed a main effect of MPH (GFW Sound Analysis, WRAT-R Arithmetic), they also showed an interaction with program status, suggesting effects may have been driven by one or more of the instructional programs (WIST for GFW Sound Analysis and GCAST and WIST for WRAT-R Arithmetic). Moreover, children who received stimulant medication treatment without concurrent reading remediation did not demonstrate significant gains in reading skills from pretest to posttest: For those children in the GCAST program, there was no significant advantage for MPH over placebo at posttest on any of the reading measures. Thus, MPH, in the absence of reading remediation, does not appear to result in a lasting improvement in reading skill for children who struggle with both reading and attention. These results are in contrast to those of Bental and Tirosh (2008), who reported a short-term and state-dependent benefit of MPH over placebo on word and nonword reading in children with ADHD+RD and of Williamson et al. (2014), who reported enhanced reading fluency as a result of receiving MPH rather than placebo. Together, this suggests that while MPH may facilitate performance on some reading tests (i.e., allow children to sustain attention in order to persist longer and be less prone to distraction in a testing situation), this benefit may not hold up over time and translate into improved reading skill in the absence of concurrent targeted reading instruction. In short, MPH in the absence of targeted reading remediation does not improve literacy learning and reading outcomes, at least not during a period of about 5 weeks.

In contrast, substantial improvements in reading outcomes were observed as a result of participating in a targeted reading intervention program (either PHAB/DI or WIST, collapsed across medication conditions). More specifically, both reading programs resulted in significant gains on standardized measures of Word Attack, comprehension skill, and the decoding of instructed words (Keywords Test) and uninstructed transfer words (Test of Transfer), that were significantly larger than that observed for children in the GCAST program. Some program-specific gains were also observed in the absence of an interaction with medication status: As expected, children in WIST ended their program with higher performance on the Keywords Test than children in either PHAB/DI or GCAST. Also as expected, children in PHAB/DI showed greater improvement on GFW Sound Analysis than children in WIST or GCAST. These effects held regardless of whether the children received MPH or placebo, suggesting that it may have been the program content itself, rather than medication, that benefited the children. Together, this suggests that children with comorbid ADHD+RD can benefit substantially from intense reading remediation. Overall, the magnitude of effects on academic outcomes was comparable to past studies involving RD children with no attentional problems. For example, Lovett et al. (1994) reported on the efficacy of the same reading interventions for children with RD (without ADHD) and found effect sizes of .36 for Keywords (present study r_effect = .42), .33 for the Test of Transfer (present study r_effect = .30), .23 for WRMT-R Word Attack (present study r_effect = .22), and .21 for GFW Sound Analysis (present study r_effect = .14).

Our results differ from those of Rabiner and Malone (2004), who report no discernible impact of phonics-based reading tutoring in Grade 1 children identified as having both reading and attention difficulties. We see three possible explanations for this discrepancy. One could be the age of the children, who were older in the present study (Grades 2–4), but representative of the mean age at which children with ADHD are referred for clinical assessment. Another could be the extent to which the reading programs were modified to address both the reading and attention needs specific to this group of children. In the current study, both reading programs were adapted to facilitate active engagement and to accommodate children’s concurrent challenges with processing speed, working memory, and selective and sustained attention. Such modifications, which Rabiner and Malone highlight as missing from their program, may be necessary to promote learning for these children. Instructor training in classroom management techniques for ADHD may also be an important factor, especially given that many children with ADHD (with or without RD) also struggle with additional comorbidities, such as oppositional defiant disorder or conduct disorder (MTA Cooperative Group, 1999).

A third possibility is that medication has a differential effect on reading outcomes depending on the content and pedagogical strategies used in the intervention program. Although it must be emphasized that our small group sizes may have underestimated medication effects in each program, we did find a moderate effect of medication status, which approached significance, for the two primary tests of word reading (Word Attack and Word ID) for children in PHAB/DI only. This medication effect was not observed for children in WIST (or GCAST). More specifically, children in PHAB/DI who received MPH ended their program with marginally higher scores on these reading tests than those who received placebo, whereas for those in WIST, scores improved regardless of medication status, and for those in GCAST, scores did not improve for either medication group. Again, a look towards the pedagogical strategies and/or program content may explain these differential effects. The PHAB/DI program focuses on promoting key phonological and word attack skills by way of direct instruction methods that include high rates of teacher modeling, cueing, structured prompts, explicit feedback, and massed practice. Conversely, the WIST program emphasizes word analysis at the larger subsyllabic level (e.g., onset/rime) as well as strategy training by way of modeling, guided practice, and discussion. As well, the WIST program incorporates a number of different activities to achieve these goals that children may find engaging (e.g., rhyming games, word challenges) as well as colorful and supportive visual cues for each strategy (Lovett et al., 1994). Given that instructional contexts that focus on higher-order “analysis and inference” skills are associated with greater engagement than lessons focusing on basic skills (Downer, Rimm-Kaufman, & Pianta, 2007), it may be that the strategies used in WIST were more successful in maintaining student engagement and promoting learning without the need for medication than those in PHAB/DI. Conversely, for those in PHAB/DI, it may be that the decrease in hyperactivity symptoms that students experienced as a result of receiving MPH promoted skill acquisition in an arguably less engaging educational context. This conclusion, however, is speculative. More research is needed to test this hypothesis in a systematic format.

Study Limitations

The main limitations of our study were the small sample sizes and attrition from the assigned medication condition prior to commencing the academic programs, both of which threaten the study’s internal validity. We had to exclude many potential participants (primarily 7-year-olds) because they did not meet full clinical diagnostic criteria for ADHD+RD. In part, this was because several of the selected reading tests exhibit psychometric problems (inadequate floor effects and step item gradients), which render them relatively insensitive to the reading problems of 7-year-olds (Bradley-Johnson & Durmusoglu, 2005). This reduced our sample size substantially and may have prevented us from detecting some additional treatment effects, particularly regarding possible potentiating effects of medication on specific educational programming. The statistical power of our study was further compromised by children changing from their assigned medication condition prior to the start of the academic instruction programs, which posed problems for analysis, particularly for interpreting differential effects of medication in the three intervention groups. Although we attempted to address this issue by using both ITT and as-treated approaches, neither can address adequately the threat to internal validity, so we caution readers to keep these caveats in mind when interpreting our findings.

Nonetheless, the treatment effects observed were noteworthy; children’s behavior and reading performance were both substantially improved, although neither was normalized. Immediate-release and longer acting medication, which were not available in Canada at the time of the study, may have further potentiated the effect of combined medication and reading remediation treatment. It also may be that a longer duration of intervention is necessary for children to experience larger gains. Indeed, Roberts et al. (2014) found that 3 years of intensive reading intervention for middle school students who struggle with both reading and attention resulted in improved and normalized reading achievement, as well as improved ratings of attention, whereas our programs were only 10 weeks. We did not include any systematic follow-up evaluation, which precludes our ability to determine whether the beneficial effects of treatment were maintained or increased over time. Future studies wishing to address this should also incorporate curriculum-based measures of reading-related skills, as they may provide a more sensitive measure of children’s response to reading instruction and rate of growth.

Future work may also benefit from investigating the effects of intervention for children with ADHD+RD at a younger age (e.g., in Grades 1 and 2) and including measures of children’s processing speed, which is considered to be a weakness shared in both ADHD and RD (Miranda et al., 2011; Pennington, 2006; Shanahan et al., 2006). Previous work has shown a positive effect of MPH on naming speed of colors in children with ADHD, a subset of whom also had RD (Tannock et al., 2000). This benefit to naming speed may account for Keulers et al.’s (2007) finding of an effect, albeit marginal, of stimulant medication on children’s reading fluency in Dutch. Future studies, examining the relative and combined effect of MPH and targeted reading instruction on attention, naming speed, and measures of reading fluency and accuracy may inform our understanding of the mechanism of treatment outcomes in children with ADHD+RD. More generally, timed measures could be helpful to address possible gains in reading fluency as a result of educational and/or pharmaceutical interventions.

In conclusion, despite this study’s limitations, our findings have important clinical, educational, and ethical implications for children with comorbid ADHD+RD. Our main findings suggest that (a) intensive reading intervention is a critical component of effective treatment for students with ADHD +RD and (b) active medication treatment, while improving the behavioral symptoms of ADHD, does not result in gains in reading ability in this comorbid group of children in the absence of concurrent reading remediation treatment. A possible potentiating role of medication in further enhancing response to reading intervention in children with ADHD+RD warrants further investigation.

Footnotes

Authors’ Note

The data for this study were collected some years ago (1996–2001), but this study was not submitted for publication at that time for various reasons, including the unexpected and untimely death of one of the co-investigators (Nancy J. Benson). It is for this reason that the currently available forms of methylphenidate and the updated Woodcock-Johnson III standardized reading measures were not used. However, we believe that despite the age of our data, this study contributes novel and important findings. The authors thank Dr. Anne-Claude Bedard, Min-Na Hockenberry, Dr. Erica Krane, Mariko Lui, Mary Masellis, Dr. Alison McInnes, and Jo-Ann Stewart for the help with data collection and management.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by an operating grant from the Canadian Institutes of Health Research (Grant No. MT 13366) and by the donation of placebo medication from Novartis Pharmaceuticals.

Notes

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