Validating a Self-Report Screen for ADHD in Early Adulthood Using Childhood Parent and Teacher Ratings

Abstract

Objective:

This article evaluates the diagnostic utility of a self-report screening tool for adults based on Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV) ADHD criteria.

Method:

Children with speech/language (S/L) impairment and typically developing controls had ADHD symptoms rated by parents and teachers at ages 5 and 12. At age 19, participants completed the Adult Attention Problems Scale (AAPS), an 18-item screen. Receiver operative characteristic curve analyses were used to assess the efficiency of this instrument in screening for ADHD.

Results:

The AAPS had moderate sensitivity and high specificity, but only for adults without a history of communication disorders.

Conclusion:

The AAPS provides clinicians with the only self-report scales for ADHD in adulthood, validated with childhood ADHD symptoms assessed by multiple raters. However, scale characteristics were poor for the S/L-impaired cohort. Given the overlap between language impairment and ADHD, adult ADHD measures validated in S/L-impaired samples are needed.

Keywords

ADHD self-report adults screening communication disorders

The diagnosis of ADHD in childhood is supported by extensive research; however, less is known about ADHD in adulthood. Longitudinal studies have shown that attention problems in childhood and adolescence persist into adulthood (Fischer, Barkley, Smallish, & Fletcher, 2002; Rasmussen & Gillberg, 2000). The prevalence of ADHD among adults has been estimated to be approximately 4% (Kessler et al., 2006). However, conclusions on the persistence of ADHD are complicated by the variations in diagnostic criteria, study-selection criteria, sample size, and age distribution, among others, that characterize research in this area (Barkley, Fischer, Smallish, & Fletcher, 2002, 2006; K. Murphy & Barkley, 1996b).

Complexities in diagnosis notwithstanding, attention problems in adulthood, as in childhood, are related to psychosocial functioning (e.g., Fischer et al., 2002). For instance, Kooij et al. (2005) reported that adults with four or more ADHD symptoms of either inattentive or hyperactive/impulsive type had greater self-perceived psychosocial impairment than adults with fewer symptoms, even after controlling for general psychopathology. Adult ADHD is associated with elevated rates of educational, employment, and marital problems; lower socioeconomic status (SES); and poorer global functioning (Barkley et al., 2006; Biederman et al., 1993; K. Murphy & Barkley, 1996b).

ADHD is also associated with considerable comorbidity. In clinical populations of adults diagnosed with ADHD, approximately 75% have one or more comorbid psychiatric conditions (Pary et al., 2002). The high prevalence of psychiatric comorbidities complicates the diagnosis of ADHD in adulthood and requires a careful differential diagnosis of other possible disorders that could include ADHD-like symptoms.

Measuring Adult ADHD

Although well-validated behavioral checklists and rating scales are widely available to assess childhood ADHD status (e.g., Achenbach, 1991a; Conners, Sitarenios, Parker, & Epstein, 1998; Erhart, Döpfner, Ravens-Sieberer, & the Bella Study Group, 2008), this is not the case for adult ADHD. A number of assessment tools for adult ADHD are available; however, there is relatively little published data on the validity and reliability of such measures.

Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association [APA], 1994) diagnostic criteria for ADHD specify that some symptoms will be present and cause impairment prior to age 7 and that impairment will be present in two or more settings. Very few prospective studies that begin in childhood and assess ADHD status over the lifetime have been reported. In fact, only four known major prospective studies of childhood ADHD have retained 50% or more of their sample size into adulthood (Fischer et al., 2002; Mannuzza, Klein, Bessler, Malloy, & LaPadula, 1998; Rasmussen & Gillberg, 2000; Weiss & Hechtman, 1993).

As a result, diagnosis of adult ADHD often relies on recollections of childhood symptoms. This has a number of methodological problems affecting research on ADHD in adulthood. Individuals who do not have significant mental health concerns are often inaccurate in their long-term recall, showing significant discrepancies between psychosocial events and issues reported at the time, and retrospective recall of these same events in adulthood (Offer, Kaiz, Howard, & Bennett, 2000). The presence of mental health concerns may further decrease accuracy. For instance, retrospective recall of childhood ADHD symptoms for adults may overrepresent the correspondence and continuity of childhood and adult ADHD symptoms, as individuals with current concerns related to ADHD may be more likely to recall examples of their childhood behavior corresponding to ADHD, whereas individuals who do not have these concerns in adulthood may be less likely to recall childhood ADHD symptoms. At the same time, the executive dysfunction associated with ADHD may increase risk of forgetting childhood symptoms (D. E. Johnson & Conners, 2002). As such, retrospective recall by adults may underrepresent the severity of the childhood stage of the disorder.

In addition, because of the paucity of validation research on adult ADHD assessments, the appropriate diagnostic threshold for ADHD in adulthood is not clear. For instance, children are more active and have greater difficulty concentrating than do adults (Kooij et al., 2005). This has led some researchers to suggest that the diagnostic threshold be set lower in adults, who might experience impairment with fewer symptoms (Barkley et al., 2002; Kooij et al., 2005). However, without longitudinal data, appropriate thresholds are difficult to establish, which compounds difficulties in determining the prognosis of childhood ADHD.

Self-report behavioral checklists are commonly used in the assessment of adult ADHD. Informant reports may be more difficult to obtain for adults than children; adults also may be more capable of reporting on their symptoms than children (Kooij et al., 2008), particularly on day-to-day functioning (Barkley et al., 2002). Many inattentive ADHD symptoms, which are particularly characteristic of adult ADHD, are not easily observable and may be better rated by the individual experiencing the symptoms, rather than an informant (P. Murphy & Schachar, 2000). Empirical results comparing self-reports to informant reports have been mixed. For instance, Belendiuk, Clarke, Chronis, and Raggi (2007) examined the concordance of diagnostic measures for ADHD, including rating scales, self-report questionnaires, and diagnostic interviews. Results demonstrated high correlations between self-reports and other means of assessment, with higher absolute levels of symptoms self-reported by young adults than by their parents. In contrast, Barkley et al. (2002) found higher levels of symptoms reported by parents than by young adult self-report, and poor agreement between self-reports and parental ratings. P. Murphy and Schachar (2000) also assessed the reliability of self-reports in adult ADHD assessment, and found that self-reported and informant-reported ratings correlated substantially (r = .59-.70).

Some of the more common questionnaires used to assess adult ADHD include the ADHD Rating Scale-IV (DuPaul, Power, Anastopoulos, & Reid, 1998), the Adult ADHD Self-Report Scale (ASRS; Adler, Kessler, & Spencer, 2003; Kessler, Adler, Ames, et al., 2005), the Attention-Deficit Scales for Adults (ADSA; Triolo & Murphy, 1996), the Conners’ Adult ADHD Rating Scales (CAARS; Conners, Erhardt, & Sparrow, 1999), and the Brown Attention-Deficit Disorder Rating Scale for Adults (BADDS; Brown, 1996). These measures include both hyperactive/impulsivity and inattention symptoms, except for the BADDS, which includes only inattention symptoms. Most scales also correspond at least in part to DSM criteria for ADHD.

Despite these strengths, an important limitation in the validation of adult ADHD measures is the measurement of childhood ADHD symptoms, which is a criterion for a diagnosis of ADHD. Very few longitudinal studies evaluate the course of ADHD in childhood through the adult years. Validation studies for the adult ADHD measures listed above have either relied on retrospective report (ADHD Ratings Scale-IV, ADSA, ASRS) or have not assessed childhood symptoms (CAARS, BADDS).

In response to the need for an effective and efficient ADHD self-report questionnaire validated with childhood data, the present study was conducted to determine the diagnostic utility of the Adult Attention Problems Scale (AAPS), an 18-item DSM-IV-based self-report questionnaire. The AAPS was administered to a sample of young adults who were part of a longitudinal study originally designed to assess the life course of speech/language (S/L) impairment. We use longitudinal data from age 5 to adulthood to assess cutoffs for adult ADHD based on self-reported ADHD symptoms and childhood ADHD ratings by parents and teachers. Receiver operating characteristic (ROC) curves are used to evaluate various thresholds for ADHD in adulthood. ROC modeling assesses how well an instrument detects its target using different cutoffs; true positives and true negatives represent correspondence between the instrument and the characteristic it is measuring; false positives and false negatives represent mismatch. A cutoff for classifying adult ADHD is selected based on the trade-off between false positives and false negatives. The optimal clinical cutoff score on a questionnaire depends on the relative importance of sensitivity and specificity for the given application.

Unlike studies relying on retrospective reports of childhood ADHD, we define ADHD using childhood parent and teacher ratings. The use of ROC analyses for ADHD is complicated by the longitudinal design as well as the theoretical underpinning of the ADHD diagnosis as a childhood-onset disorder, such that adult-onset ADHD (without childhood symptoms) is conceptually excluded. Defining childhood ADHD (significant ADHD symptoms) as the gold standard for an adult ADHD measure, false positives (no childhood ADHD, adult ADHD) are likely to be errors and should be minimized. In contrast, false negatives (childhood ADHD, no adult ADHD) may represent either errors (missed “true” cases), or remission and/or improvement of ADHD symptoms to nonclinical levels. These false negative cases may not be errors but “true remissions.” Given the paucity of data on longitudinal outcomes of childhood ADHD, it is not clear what proportion of children with ADHD would be expected to continue to meet criteria in adulthood, but a substantial proportion might be expected to “outgrow” the disorder or improve to subclinical levels. Nevertheless, although optimizing both sensitivity and specificity makes sense for many efficiency analyses, the optimal cutoff for an adult ADHD screen using childhood ADHD as the criterion would likely prioritize specificity (reducing false positives), at the expense of sensitivity.

DSM-IV criteria for adult ADHD include “some hyperactive-impulsive or inattentive symptoms that caused impairment were present before age 7 years” (APA, 2000, p. 78). However, many ADHD symptoms are common among typical children and may not reflect a clinical condition; and some symptoms common to different mental health concerns may not reflect ADHD. Therefore, a threshold is needed to meaningfully distinguish individuals with and without evidence of early-onset ADHD. Although the DSM diagnostic criterion does not explicitly require that ADHD symptoms before age 7 occur in multiple settings, the multiple-settings criterion is used in the diagnosis of childhood ADHD to distinguish symptoms of ADHD from typical behavior (including behavior limited to a specific context) or behavior related to concerns other than ADHD. Therefore, we defined childhood ADHD symptoms using ratings from both parents and teachers.

Included in the DSM criteria is onset of symptoms by age 7. In the current study, we use parent and teacher ratings collected at age 5 and age 12. The age 5 ratings do not capture the entire period before age 7. Moreover, the shift from kindergarten to the increased demands for prolonged concentrated seat work in first grade may result in more children being identified with ADHD symptoms; these children would be missed in the age 5 assessment. Therefore, we included reports from young or middle childhood (age 5 or 12) as evidence of childhood ADHD symptoms.

The clinical cutoff we selected is at or above the 90th percentile rating by parents at age 5 or 12 and at or above the 90th percentile rating by teachers at age 5 or 12. Although a clinical (90th percentile) rating was required from both parents and teachers, the ratings did not need to be concurrent. These criteria were intended to be severe enough to select children whose behavior was reasonably likely to be related to ADHD, yet be lenient enough so as not to miss children with significant ADHD symptoms, who may in fact have met criteria for ADHD at some point in childhood, even if not at age 5 or age 12 assessments.

ADHD and Language Impairment

ADHD is one of the most common psychiatric disorders among children with language impairments (Baker & Cantwell, 1987; Beitchman, Nair, Clegg, Ferguson, & Patel, 1986; Beitchman, Wilson, Brownlie, Walters, & Lancee, 1996; Snowling, Bishop, Stothard, Chipchase, & Kaplan, 2006). Conversely, language impairment is common among youth with ADHD (Biederman et al., 2006; Bruce, Thernlund, & Nettelbladt, 2006; Cohen, Davine, Horodezky, Lipsett, & Isaacson, 1993; Cohen et al., 1998; Geurts & Embrechts, 2008; Wassenberg et al., 2010). Language impairment tends to persist to adulthood (C. J. Johnson, Beitchman, et al., 1999); therefore effective ADHD assessment tools for adults with and without S/L impairment are important to meet the needs of adults with attention problems, including those with comorbid attention and communication difficulties.

This research is part of a longitudinal study following a group of children identified with S/L impairment, and a matched control group, into adulthood. The S/L-impaired cohort and controls were identified from a screening and S/L assessment from a one-in-three random sample of 5-year-olds living in Ottawa, Canada. This sample allows us to assess the relative efficacy of such an instrument for adults with and without language impairment, which is important because individuals with language impairment are disproportionately likely to have attention problems and to meet criteria for ADHD (Baker & Cantwell, 1987; Beitchman et al., 1996; Beitchman, Nair, Clegg, & Patel, 1986; Cohen et al., 1998). Except for direct comparisons of S/L groups, results are controlled for S/L status and/or weighted to approximate a representative sample, to increase generalizability of the results.

Method

Participants

Two hundred eighty-four participants (180 boys and 104 girls) were part of the Ottawa Language Study (OLS), a multiwave longitudinal study. The original cohort was a one-in-three random sample of all 5-year-old, English-speaking kindergarten children (n = 1655) in the Ottawa–Carleton region of Ontario, Canada, in 1982 (Beitchman, Nair, Clegg, & Patel, 1986). Using a staged screening and assessment process, qualified speech–language pathologists identified 142 children with S/L impairments. A control sample of 142 children matched for age, sex, and school was simultaneously recruited. Follow-up reassessments were conducted when participants were aged 12 (Wave 2) and 19 (Wave 3). Parents (Waves 1 and 2) and participants (Wave 3) completed consent forms after study procedures were explained. All procedures were approved by the institutional ethics review boards of the Royal Ottawa Hospital (Wave 1) and the University of Toronto (Waves 2 and 3). Participation rates at Waves 2 and 3 were 86% and 91%, respectively.

The 205 participants (135 boys, 70 girls) who had sufficient data at age 5, 12, and 19 for inclusion in the present study ranged in age from 18 to 20 years (M = 18.88, SD = 0.39). Two thirds were in school. Mean current grade (or highest grade achieved, for participants not in school) was 11.73 (SD = 1.07).

Measures

Psychiatric diagnoses and mental health

Age 19 psychiatric disorders other than ADHD were assessed using (a) the University of Michigan version of the Composite International Diagnostic Interview (UM-CIDI; Kessler et al., 1998; Wittchen, 1994), a modification of the CIDI (World Health Organization, 1990) designed to improve its efficiency and assessment capability and (b) the Global Assessment of Functioning (GAF) Scale (APA, 1994). Using the UM-CIDI, the following psychiatric disorders based on DSM-III-R (APA, 1987) criteria were assessed: affective disorders, anxiety disorders, and substance-use disorders. Eating disorders and schizophrenia were also assessed but are not included here due to extremely low prevalence in this sample. The UM-CIDI was also used to assess antisocial personality disorder and conduct disorder consistent with DSM-IV (APA, 1994) criteria. GAF scores were used to assess impairment; diagnoses were assigned to participants who met both diagnostic criteria on the CIDI and had a GAF score less than 70, reflecting at least mild functional impairment.

Childhood ADHD status

Parent ratings at ages 5 and 12 on the Child Behavior Checklist (CBCL) Attention Problems Scale (Achenbach, 1991a) and teacher ratings at ages 5 and 12 on the Conners Teacher Rating Scale (CTRS; Trites hyperactivity factor; Conners et al., 1998; Trites, Blouin, & Laprade, 1982) were combined to determine childhood ADHD status. Scores at or above the 90th percentile on the CBCL at age 5 or 12 were classified as clinical according to parent report; scores at or above the 90th percentile on the CTRS at age 5 or 12 were classified as clinical according to teacher report. To be classified as positive for childhood ADHD, children had to have at least one clinical rating according to parent report (age 5 or 12) and teacher report (age 5 or 12). For example, a child classified as clinical on the CBCL Attention Problems Scale at age 5 and the CTRS hyperactivity factor at age 12 would be classified as positive for childhood ADHD. Participants were excluded from analyses if they did not have either a valid test score for three of the ratings or two clinical ratings from different sources (parent and teacher).

No direct measure of impairment was included in the definition of childhood ADHD. However, to verify that the definition of childhood ADHD was associated with significant impairment, participants who met criteria for childhood ADHD and participants who did not meet criteria for childhood ADHD were compared on three measures related to impairment: the Adaptive Functioning Scale of the age 12 Teacher’s Report Form (Achenbach, 1991b), the Social Competence Scale of the age 12 CBCL (Achenbach, 1991a), and rates of high school noncompletion. All analyses were controlled for S/L impairment and SES. Participants who met criteria for childhood ADHD had poorer scores on adaptive functioning (M = 38.68, SD = 8.19) than participants who did not meet criteria (M = 49.25, SD = 9.00), Wald χ²(1) = 13.51, p < .001. Similarly, participants who met criteria for childhood ADHD had poorer scores on social competence (M = 33.68, SD = 8.09) than those who did not meet criteria (M = 46.20, SD = 10.53), Wald χ²(1) = 17.66, p < .001. Median scores for adaptive functioning (median = 36) and social competence (median = 33) for participants who met criteria for childhood ADHD fell within the clinical range. Participants who met criteria for childhood ADHD were also more likely to leave high school before completion (35%) than those who did not meet criteria (6%), Wald χ²(1) = 9.56, p < .002.

The AAPS

The instrument used to assess ADHD in young adulthood (age 19), the AAPS is an 18-item scale based on the DSM-IV criteria for ADHD that rates symptom frequency on a Likert-type scale ranging from 1 (never ) to 4 (often). Responses were summed, with a maximum total score of 72. The 18 items on the AAPS correspond to the 18 domains of DSM-IV ADHD symptoms.

Demographics

When participants were 5 years old, parents were interviewed about their child’s history, family background, and demographics. SES was measured using occupational status ratings based on Blishen, Carroll, and Moore (1987). At age 19, participants completed a comparable interview that included questions about education history.

Statistical Analysis

Internal consistency of the scale was assessed via Cronbach’s alpha. We also computed Cronbach’s alpha with the removal of one item at a time to assess whether internal consistency would be higher with one or more items deleted.

ROC curve modeling was used to determine the trade-off between false positive and false negative test results to determine the optimal cutoff on the ROC curve for the classification of ADHD at age 19, with childhood ADHD status as the state variable or gold standard. Sensitivity (proportion of participants positive for ADHD in childhood scoring at or above the AAPS cutoff) and specificity (proportion of participants not positive for childhood ADHD scoring below the AAPS cutoff) efficiency statistics were calculated for various cutoff scores on the AAPS. In addition, positive predictive power (proportion of the participants scoring at or above the AAPS cutoff who are positive for childhood ADHD) and negative predictive power (proportion of the participants scoring below the AAPS cutoff who are negative for childhood ADHD) were also calculated. Although sensitive to prevalence rates, positive and negative predictive power give important information on scale utility, particularly for clinicians interpreting scale results. Logistic regression was used to assess divergent and convergent validity of the AAPS, controlled for possible confounds (S/L impairment and SES).

Results

Scale Characteristics

Internal consistency

Internal consistency of the AAPS scale was high (Cronbach’s α = .87). Cronbach’s alpha with one item removed did not identify items reducing internal consistency (α’s ranged from .857 to .872).

Sensitivity and specificity analysis

ROC curves were generated for the typical language controls and the S/L-impaired participants (see Figure 1). Combined estimates of sensitivity and specificity, weighted to reflect estimated prevalence of S/L impairment (5%) based on estimated rates reported in DSM-IV (APA, 1994), were also computed. Using the strategy of maximizing specificity, while maintaining adequate sensitivity, we chose a cutoff score of 48, which corresponded to a moderate weighted sensitivity of .62 and a high weighted specificity of .89. Sensitivity and specificity of the AAPS were higher among the typical language sample (sensitivity = .63; specificity = .88) than in the S/L-impaired sample (sensitivity = .33; specificity = .85). Area under the curve (AUC) was also much higher for the typical language controls (AUC = .803, p < .004); the AAPS did not exceed chance in its ability to detect childhood ADHD in the S/L-impaired group (AUC = .628, p = .120).

Figure 1.

Receiver operating characteristic curve analysis by speech/language group

Using the selected cutoff of 48, 14% of the typical language controls and 19% of the S/L-impaired cohort met criteria for adult ADHD. Correcting for oversampling of S/L-impaired participants, the weighted estimated prevalence for adult ADHD was 14.3%. Adding an impairment criterion (GAF scores less than 70), the weighted prevalence estimates falls to 7.6.

Predictive Power

At the selected cutoff of 48, positive predictive power (proportion of “true positives” among those exceeding the cutoff on the questionnaire) was .26 for the controls and .28 for the S/L-impaired cohort. Negative predictive power (proportion of “true negatives” among those not exceeding the cutoff) was .97 for controls and .88 for the S/L-impaired cohort.

Comorbidity and Convergent and Divergent Validity

Adult ADHD (clinical rating on the AAPS) was significantly comorbid with other DSM-IV psychiatric disorders. Results of logistic regressions, controlled for S/L-impairment status, are shown in Table 1. Individuals above threshold for adult ADHD had increased odds of various types of diagnoses, ranging from 5.86 for conduct disorder to 3.10 for affective disorder. Using Bonferroni adjustments for multiple comparisons (family-wise α = .05), all odds ratios (OR) were significant with the exception of affective disorders.

Table 1.

Logistic Regression: Comorbid Diagnoses Predicting Adult ADHD Status

Diagnosis	Odds ratio^a	95% CI for odds ratio	Wald χ²(1)	p
Any psychiatric disorder	3.29	[1.59; 6.80]	10.40	.001*
Conduct disorder	5.38	[2.52; 11.52]	18.81	.001*
Antisocial personality disorder	4.12	[1.78; 9.57]	10.90	.001*
Affective disorder	3.01	[1.23; 7.40]	5.80	.016*
Anxiety disorder	3.95	[1.73; 9.04]	10.61	.001*
Substance-use disorder	4.79	[2.11; 10.86]	14.03	.001*

Note: CI = confidence interval. Adult ADHD includes those participants scoring 48 or above on the Adult Attention Problems Scale.

Based on bivariate logistic regression analysis controlling for speech/language cohort.

p < .05, family-wise (Bonferroni corrected) a.

GAF scores were also compared by adult ADHD status. Participants who exceeded the cutoff for adult ADHD had lower GAF scores (M = 64.73, SD = 11.96) than adults with fewer adult ADHD symptoms (M = 73.66, SD = 11.85), controlled for SES and S/L status, OR = 1.05, 95% confidence interval (CI) = [1.02, 1.08], Wald χ²(1) = 9.973, p < .003. A GAF score below 70 indicates at least mild functional impairment.

Convergent validity was further assessed by observing the pattern of correlations of the AAPS with educational and cognitive correlates of ADHD (see Table 2). Because of the high correlation and conceptual overlap of S/L status with both IQ and educational attainment (Barkley et al., 2006; Beitchman et al., 1989, 1996; Young et al., 2002), analyses were conducted separately for the two groups. Among the controls, scores in the clinical range on the AAPS were significantly associated with lower age 5 verbal IQ, Wald χ²(1) = 4.371, p = .037, and marginally less attained education by age 19, Wald χ²(1) = 3.827, p = .050. These differences were not significant among the S/L-impaired cohort.

Table 2.

Age 5 IQ and Adult Educational Attainment by Self-Reported Adult ADHD

	ADHD+		ADHD−		Wald χ²(1)	p
	M	SD	M	SD	Wald χ²(1)	p
Age 5 full scale IQ
Speech/language impaired	102.61	10.43	101.97	14.61	0.981	.322
Controls^a	113.84	10.35	120.10	11.33	4.371	.037
Highest grade achieved
Speech/language impaired	11.22	1.41	11.52	1.06	0.05	.820
Controls^b	11.37	1.34	11.96	1.03	3.83	.050

Note: ADHD+ group scored at or above the cutoff of 48 on the Adult Attention Problems Scale (AAPS); ADHD– group scored below 48 on the AAPS. Sample size for speech/language-impaired sample—ADHD+: n = 23, ADHD–: n = 95; sample size for controls—ADHD+: n = 19, ADHD–: n = 115.

Odds ratio (1 SD lower IQ) = 2.34, 95% confidence interval = [1.05, 5.18].

Odds ratio (one grade) = 1.54, 95% confidence interval = [1.00, 2.36].

Discussion

The objective of this study was to validate a self-report screen for ADHD based on childhood ADHD status. We defined childhood ADHD with widely used, well-validated questionnaires (Chen, Faraone, Biederman, & Tsuang, 1994). The AAPS demonstrated moderate sensitivity and high specificity, and showed evidence of convergent and divergent validity for young adults without a history of communication disorders. In contrast, this instrument may not be valid for use with individuals who have a history of communication disorders given the poor sensitivity within this cohort.

At the selected cutoff, the AAPS had a weighted sensitivity of .62 and weighted specificity of .89. These efficiency statistics are comparable with those reported for the ADSA (sensitivity, specificity = .58, .94 for the conservative cutoff; .71, .82 for a liberal cutoff; West, Mulsow, & Arredondo, 2007), the Conners Adult ADHD Ratings Scales (sensitivity, specificity = .71, .75), and the ASRS (sensitivity, specificity = .56, .98), despite the time lag between the childhood ADHD assessment (age 5 and/or 12) and the screen (age 19). We chose a cutoff score of 48, which had relatively good specificity and moderate sensitivity, among the typical language sample. A high specificity was necessary in this study because the gold standard was childhood ADHD; childhood ADHD symptoms causing impairment is a criterion for adult ADHD. Although the definition of childhood ADHD utilized as the gold standard in this study may be more severe than the level of childhood symptoms required for a diagnosis of adult ADHD; nevertheless, we expected improvements to nonclinical levels (defined as false negatives) to be more common than adult ADHD cases with subclinical childhood symptoms (defined as false positives), and we selected the cutoff accordingly. Minimizing the number of false positives is also important because inaccurate diagnosis of ADHD may delay assessment and treatment of other psychiatric conditions that share some of the same features as ADHD.

Based on the predictive power statistics, for both the S/L-impaired and control groups, but particularly the controls, a score below the selected cutoff on the AAPS was effective in ruling out ADHD (defined as significant childhood ADHD symptoms in home and school settings). As with many screening tools, positive results on the scale suggest further investigation; one quarter of those exceeding the cutoff in the current sample had significant ADHD problems starting in childhood and may have behavioral issues that reflect ADHD.

Using the AAPS to define adult ADHD, the prevalence was 14% without an impairment criterion. Adding the impairment criterion (GAF < 70), the prevalence rate of 7.6 was closer to, while still exceeding, prevalence rates for childhood ADHD (APA, 2000). Because of comorbidity, it is not clear to what extent impairment was due to ADHD or due to other disorders. Prevalence would be reduced further if ADHD-specific impairment were included as a criterion.

Validation of this measure was conducted on the assumption that relatively few individuals grow out of their ADHD by late adolescence. This resulted in a more conservative test; sensitivity was underestimated by counting as false negatives the individuals who met criteria for childhood ADHD but would no longer meet criteria for ADHD in adulthood, even with a more comprehensive assessment (i.e., remitters). Follow-up studies vary widely in the proportion of children with ADHD defined as continuing to meet criteria in late adolescence/early adulthood, with estimates of approximately 50% to 70% of children with ADHD no longer meeting criteria (Fischer et al., 2002; Halperin, Trampush, Miller, Marks, & Newcorn, 2008). If we assume conservatively that 20% to 30% of children with ADHD outgrow their ADHD by late adolescence, many cases designated as false negatives in this study would in fact constitute true negatives, and consequently, the efficiency statistics for this instrument would correspondingly improve.

ADHD and Impairment in Functioning

Consistent with previous research (K. Murphy & Barkley, 1996a; Torgersen, Gjervan, & Rasmussen, 2006), adults with ADHD in our sample were more impaired than adults without ADHD. Unfortunately, we were not able to assess a number of other important measures of functioning such as occupational performance. K. Murphy and Barkley (1996a) found that adults with ADHD had significantly more employment difficulties compared with controls. Future studies should aim to investigate multiple indicators of impairment in functioning from diverse areas of participants’ lives.

In addition to impairment in daily functioning, our results indicate that individuals with ADHD in adulthood also experience impairment as a result of numerous comorbid disorders. These comorbidities were similar to those found in other research on adult ADHD (Biederman et al., 1993; Kessler, Adler, Barkley, et al., 2005; Kessler et al., 2006; K. Murphy & Barkley, 1996b). ADHD and other comorbid conditions may share features such as reduced stress tolerance and emotional dysregulation (Sobanski, 2006). Symptom overlap complicates matters for clinicians, as it is very difficult to ascertain the relative contribution of an individual’s ADHD symptoms or comorbid disorder(s) to their daily impairment. Given the high rates of comorbidity, it is important for clinicians to attend to other diagnoses as well as ADHD symptoms.

ADHD and Communication Disorders

The characteristics of the sample allowed us to assess the performance of this screening measure in adults with and without a history of S/L difficulties. The AAPS had good sensitivity and specificity in the control group, given the elapsed time between measures; however, this instrument performed poorly in the S/L-impaired sample. In particular, sensitivity was low in the S/L-impaired group, indicating that the S/L-impaired participants with childhood ADHD symptoms tended not to rate themselves as having ADHD symptoms in adulthood. There are a number of possible explanations for the small proportion of individuals who met criteria for ADHD exceeding the screening threshold at age 19. First, it is possible that for some children, behavior problems related to difficulties in comprehension or verbal expression might have been misinterpreted as symptoms of ADHD. In that case, these participants would constitute “true negatives,” rather than false negatives. Second, because of the concomitant academic difficulties associated with S/L impairment (Young et al., 2002), young adults with S/L impairment may select educational programs and/or employment that does not require extensive language-based study or outputs requiring sustained attention. In contrast, typical language participants engaged in academically rigorous programs with high academic standards may be more bothered by symptoms of inattention and may be more likely to rate these as problematic. Third, concordance between self-report and reports from parents or other informants appears to increase with age in early adulthood. Good agreement between participants and their parents or other informants has been reported for individuals above the age of 30 (K. Murphy & Barkley, 1996a; P. Murphy & Schachar, 2000); however, agreement has been lower among younger adults, who tend to report fewer and less severe symptoms in comparison with parents or other informants, particularly in clinical samples (e.g., Barkley et al., 2002; Kooij et al., 2008). It is possible that the poor performance of the scale among the S/L-impaired sample was due in part to the young adults with a history of S/L impairment underreporting their ADHD symptoms. Finally, it is also possible that the language-impaired sample had more difficulty using the rating scale or assessing their own behavior.

Given the overlap between ADHD and language impairment (Beitchman et al., 1996; Biederman et al., 2006; Snowling et al., 2006), the persistence of language impairments into adulthood (C. J. Johnson, Beitchman, et al., 1999), and the fact that language impairments may not be identified (Cohen et al., 1993, 1998), these results are broadly relevant to clinicians working with adults who have ADHD symptoms. The results underscore the need for valid measures of ADHD for S/L-impaired individuals across development, and the need for further validation of new and existing measures of ADHD with S/L-impaired samples. Finally, it is important to note that the speech and language impairments in our sample were often relatively mild (C. J. Johnson, Taback, Escobar, Wilson, & Beitchman, 1999). Individuals similarly impaired may be overlooked by the untrained examiner and consequently misdiagnosed as having ADHD. It is important for clinicians to be alert to these considerations.

Strengths and Limitations

A number of studies have used similar questionnaires based on DSM-IV criteria for ADHD (e.g., Erhardt, Epstein, Conners, Parker, & Sitarenios, 1999; P. Murphy & Schachar, 2000). This study is unique, however, as it is longitudinal in design and childhood ADHD status was assessed during childhood, based on multiple informants. This is consistent with DSM-IV criteria for a childhood diagnosis of ADHD (symptoms in two different settings and impairment) and recommendations for assessment of ADHD (American Academy of Pediatrics, 2000; Tripp, Schaughency, & Clarke, 2006). As far as we know, our study is the first to validate a self-report ADHD questionnaire based on combining results from teacher and parent reports of childhood ADHD status. All other adult self-report questionnaires that are currently used to assess adult ADHD rely either on retrospective recall of childhood ADHD symptoms or clinical interview in adulthood as their “gold standard” for assessing ADHD status.

In addition to following DSM-IV diagnostic criteria, each of the 18 items on our questionnaire corresponds to one of the 18 DSM-IV ADHD-symptom criteria. Although this can be seen as a strength of the AAPS, it is important to recognize that DSM-IV criteria for ADHD were developed for children, and the scale items on the AAPS have not been adjusted for adult populations and may therefore provide a limited assessment of adult ADHD (Belendiuk et al., 2007; Riccio et al., 2005). In addition, the AAPS relies on the reports of the young adults only; parent, teacher, or other informant ratings were not available for corroboration in adulthood. Again, although high concordance between self-report and other informant reports has been reported for adults in their 30s (K. Murphy & Barkley, 1996a), concordance between self-reported ADHD symptoms and ratings by other informants are lower for younger adults (Barkley et al., 2002; P. Murphy & Schachar, 2000). In addition, participants were selected from a study originally designed to investigate longitudinal outcomes of S/L impairment in children, not ADHD. To adjust for this sampling frame, S/L impairment was controlled in some analyses; other analyses were conducted separately for the two groups. The AAPS cutoff was selected based on sensitivity and specificity statistics weighted to correct for oversampling of S/L-impaired participants. We used weights based on the 5% prevalence of S/L disorders as stated in the DSM-IV (APA, 1994); however, there is no consensus on the prevalence of speech and language impairment in children.

Participants in this study resided in the Ottawa–Carlton region when they were 5 years of age; all were between the ages of 18 and 20 in the current study. Early assessment and diagnosis enables individuals with ADHD to make treatment decisions and be aware of their symptoms before entering postsecondary education, applying for a job, starting a family, or any other major life changes that may be made more difficult by ADHD symptoms. However, further validation of ADHD self-report scales, including the AAPS, are needed across adult age groups. Furthermore, because of local demographics at the beginning of the study, most participants (approximately 90%) were White (Beitchman, Nair, Clegg, & Patel, 1986). These characteristics also reduce the generalizability of our study results. Future studies in this area should aim to select a more varied study sample, with a greater range of ages, ethnicities, and geographical locations.

Clinical Implications

An assessment of ADHD should be multidimensional, involving the use of objective measures such as behavioral checklists and rating scales, and incorporating data from multiple reporting sources and structured interviews. No single scale or test can be used to diagnose ADHD. Assessments should also assess impairment specifically associated with ADHD symptoms, rule out other psychiatric disorders that could serve as possible explanations for the adult’s symptoms, and assess for possible comorbid conditions (Erhardt et al., 1999). However, if sufficiently reliable and valid, self-report scales can be useful for initial screening purposes.

Results of this study show that the AAPS appears to be a reliable and valid screening tool for assessing ADHD in early adulthood among individuals without a history of communication disorders. However, valid measures for diagnosing ADHD in individuals with communication disorders are still needed. This is relevant to all clinicians working with adults with ADHD symptoms given that language disorders are a common but subtle correlate of ADHD. Existing measures should be used with caution with this population, or with individuals for whom S/L impairment has not been ruled out, as individuals may not be aware of their own communication difficulties.

Footnotes

Acknowledgements

We thank Brenda Cavanagh, Ron Vida, and the Ottawa Language Study team. We particularly thank our study participants and their families for making this research possible.

Declaration of Conflicting Interests

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

Funding

The author(s) disclosed receipt of the following financial support for the research and/or authorship of this article: This research was supported by grants from Health Canada, Grant 6606-5639-102, and the Canadian Institutes for Health Research, grant MOP 84421.

Bios

E. B. Brownlie, PhD, is a developmental psychologist and project scientist in the Child, Youth, and Family Program at the Centre for Addiction and Mental Health, and assistant professor of psychiatry, University of Toronto. Her research interests include gender, developmental psychopathology, and emerging adulthood.

Kim Lazare, BHS, received her honors bachelor of health sciences degree from McMaster University in 2008. She is currently in her 2nd year of medical school at the University of Toronto.

Joseph Beitchman, MD, FRCP(C), is a clinical director of the Child, Youth, and Family Program of the Centre for Addiction and Mental Health, and professor and head of the Division of Child Psychiatry at the University of Toronto. His research interests include communication disorders, child and youth psychopathology, risk factors, and child and adolescent externalizing behavior disorders.

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