Gender Differences in the Relationship Between Changes in ADHD Symptoms,Executive Functions,and Self- and Parent-Report Depression Symptoms in Boys and Girls With ADHD: A 2-Year Follow-Up Study

Abstract

Objective: This study was conducted to investigate the association between changes in ADHD symptoms, executive functions (EFs), and depression symptoms in girls and boys with ADHD over a 2-year period. Method: Thirty-six girls and 39 boys with ADHD, 18 typically developing (TD) girls and 29 TD boys (ages 9-16) were included. Assessments of EFs, ADHD symptoms, and self- and parent-report of depression symptoms were carried out. Results: For girls, a reduction of inattention symptoms was associated with a decline in parent-rated depression symptoms. A reduction in hyperactivity/impulsivity was associated with a reduction in self-rated depression symptoms in boys, and an increase in girls. A reduction in inattention symptoms was associated with a modest increase in self-rated depression symptoms in both boys and girls. Conclusion: Gathering information from both the parents and the child with ADHD is important in determining how gender may be influencing symptom profiles.

Keywords

ADD/ADHD gender executive function internalizing comorbidity longitudinal study

Introduction

ADHD in children and adolescents is associated with numerous developmental, cognitive, emotional, social, and academic impairments in addition to the core symptoms of ADHD (Becker, Roessner, Breuer, Döpfner, & Rothenberger, 2011). The prevalence of ADHD in boys is two- to ninefold higher than in girls in clinical samples and two- to threefold higher in epidemiologic samples (Nussbaum, 2012).

ADHD Symptoms and Gender Differences in Children With ADHD

Whether gender differences exist in the impairment associated with ADHD is unclear due to the low number of studies and inconsistent findings (Elkins, Malone, Keyes, Iacono, & McGue, 2011). In a cross-sectional study of children 6 to 17 years, females with ADHD were reported to have fewer hyperactive/impulsive symptoms and more inattentive symptoms compared with male counterparts (Biederman, Kwon, et al., 2005). Females with ADHD often present more commonly with the inattentive subtype than do boys (Hinshaw, Owens, Sami, & Fargeon, 2006).

Executive Functions (EFs) and Gender Differences in Children With ADHD

A large number of studies have documented cognitive deficits in children and adolescents with ADHD, particularly in EFs (Seidman, 2006; Willcutt, Doyle, Nigg, Faraone, & Pennington, 2005). Several theoretical accounts propose that EFs are a “top-down” system responsible for inhibition, working memory, and cognitive flexibility (Diamond, 2013). Multiple studies have found that although aspects of EFs are moderately correlated, they are nonetheless separable (i.e., have unique components; Miyake et al., 2000; Snyder, 2013). In a review, Seidman et al. (2005) concluded that gender differences do not exist regarding EFs deficits in ADHD.

Internalization and Externalization Symptoms and Gender Differences in Children With ADHD

Adolescent females with ADHD are also reported to suffer from more internalizing symptoms (e.g., withdrawal, somatic complaints, and anxiety/depression symptoms) than their male counterparts (Quinn, 2008). Furthermore, a review of the literature has shown that adolescent girls with ADHD have lower self-efficacy and poorer coping strategies than adolescent boys with ADHD (Rucklidge, 2010). Boys with ADHD are more likely to exhibit externalizing disorders such as oppositional defiant disorder and conduct disorder during early childhood than girls with ADHD (Roy, Oldehinkel, Verhulst, Ormel, & Hartman, 2014). However, a community-based study of children aged 4 to 17 reported no significant Gender × ADHD interactions for disruptive behavior, mood, and anxiety disorders (Bauermeister et al., 2007).

Longitudinal Studies of Gender Differences in ADHD Symptoms in Children With ADHD

In both boys and girls aged 8 to 16, symptoms of ADHD decreased in severity with age in parallel with cerebral maturation in adolescence, and ADHD hyperactive-impulsive symptoms declined at a greater rate than inattentive symptoms (Pingault et al., 2015).

A 2-year longitudinal study of 1,478 children aged 6 to 18 years with ADHD across 10 European countries did not find evidence of important sex differences in symptoms in children with ADHD (Nøvik et al., 2006). Monuteaux, Mick, Faraone, and Biederman (2010) reported that boys and girls exhibited a similar course of ADHD symptomatology during a 4- to 10-year follow-up.

Longitudinal Studies of Gender Differences in Development of EFs in Children With ADHD

EFs normally develop throughout childhood and adolescence and are not fully matured until early adulthood (Gogtay et al., 2004). Despite improved EFs performance through childhood in boys and girls with ADHD, EFs seem to remain significantly impaired into adolescence and adulthood (Seidman, 2006; Skogli, Andersen, Hovik, & Øie, 2014). Longitudinal studies have reported comparable developmental trajectories in EFs for boys and girls with ADHD (Seidman, 2006; Skogli et al., 2014).

Longitudinal Studies of ADHD Symptoms, EFs, Depression Symptoms, and Gender Differences in Children With ADHD

Follow-up studies of females with ADHD have reported that the majority of girls with ADHD continue to struggle with functional impairments across multiple domains (Biederman, Petty, O’Connor, Hyde, & Faraone, 2012; Fontaine et al., 2008; Hinshaw et al., 2006; Monuteaux, Faraone, Gross, & Biederman, 2007). Monuteaux et al. (2010) conducted two identically designed, longitudinal, case-control family studies of male and female probands with and without ADHD and their siblings (n = 471, M_age = 11.5 ± 4.3 years at baseline). Their findings indicated that although the course of ADHD across childhood and adolescence did not differ between males and females, patterns of psychiatric comorbidity were conditional on gender. The female sample demonstrated greater stability in comorbid psychopathology from childhood into adolescence (Monuteaux et al., 2010).

In a prospective follow-up study of girls with ADHD into early adulthood, internalizing symptoms and self-harmful behavior were particularly salient for girls (Hinshaw et al., 2012). Lahey and colleagues (2007) found significant interactions with time indicating that ADHD in girls (followed in 8 years from the age of 4-6) predicted more steeply rising symptoms of anxiety and depression during early adolescence than in boys with ADHD (Lahey et al., 2007). Roy, Hartman, Veenstra, and Oldehinkel (2015) found in children (M_age = 13.6 years) that peer dislike and victimization explain the prospective association between ADHD and depression, particularly in girls. They stated that symptoms and behaviors of ADHD in girls are considered gender inappropriate and are less well tolerated by peers than ADHD symptoms and behaviors in boys. This may give rise to more negative appraisals by peers and in turn increase the risk of depressive outcomes in girls (de Boo & Prins, 2007). Girls between 10 and 11 years have been found to be more sensitive to peer opinions than boys (Bakker, Ormel, Verhulst, & Oldehinkel, 2010). The research on gender differences in follow-up studies of children with ADHD is not consistent. The above-mentioned 2-year longitudinal study conducted by Nøvik and colleagues (2006) did not find evidence of important gender differences in psychiatric comorbidity in children with ADHD (Nøvik et al., 2006). One reason for the inconsistency among the studies may be that clinical research on ADHD has involved predominantly male participants because boys with ADHD are more likely to be referred to psychiatric treatment (Nøvik et al., 2006). Thus, fewer studies have compared boys and girls with ADHD in the same study. Furthermore, many studies suffer from small sample sizes, differences in diagnostic procedures, and possible rater influences (Rucklidge, 2010).

Executive processes play an important role in a child’s ability to control their thoughts, behavior, and emotions (Anderson, 2002). EFs are important for successfully navigating nearly all of our daily activities. EFs have been linked to the successful performance of a wide range of tasks, including academic performance and social functions (Rinsky & Hinshaw, 2011). A growing literature demonstrates an inverse relationship between effortful control, the ability to deliberately shift attention and inhibit behavior, and symptoms of depression in children and adolescents (see Seymour, Chronis-Tuscano, Iwamoto, Kurdziel, & Macpherson, 2014).

Problems with EFs may manifest as difficulties focusing attention at school or in everyday life, minimizing interference from irrelevant stimuli, setting and achieving goals, changing perspective, and controlling impulses (Diamond, 2013). Impairments in EFs may thus have serious consequences for quality of life, which in turn may lead to depression symptoms.

It is unclear whether symptoms of depression may also cause impairments in EFs. However, problems with EFs have been found to predict the development of later externalizing and internalizing problems in community samples of first- and second-grade children (Riggs, Blair, & Greenberg, 2003). Furthermore, interventions targeting EFs in elementary school students prevent the development of later internalizing and externalizing psychopathology (Riggs, Greenberg, Kusche, & Pentz, 2006). Thus, it is likely that reduced EFs may cause depression symptoms.

One study found that impaired inhibition was associated with poor emotion regulation in boys aged 6 to 11 years with ADHD (Walcott & Landau, 2004). For example, if a boy is prone to negative affect and exhibits low inhibitory control, he may have difficulty attenuating negative thoughts (e.g., rumination) and may exhibit negative withdrawal, possibly predisposing him to depression (Yap et al., 2011). Surprisingly, little is known about the relationship between EFs and emotional outcomes in girls with ADHD. However, a study found that better working memory and planning skills were associated with a lower incidence of psychopathology in 6- to 12-year-old girls both with and without ADHD (Rinsky & Hinshaw, 2011). Optimal social interaction may depend on an intact working memory function (Rinsky & Hinshaw, 2011). Because the sample in the study was entirely female, the findings cannot be assumed to generalize to boys with ADHD.

Seymour and colleagues (2014) examined the longitudinal relationship between ADHD symptoms and depression symptoms in a community sample of 277 youth, ages 9 to 12 (56% male). They did not demonstrate a significant relationship between gender and ADHD symptoms and depression symptoms. Their findings may be related to overall low base rates of ADHD and depression symptoms in their sample. As far as we know, no studies have investigated the relationship between changes in ADHD symptoms, changes in EFs, and changes in depression symptoms in boys and girls with ADHD.

Study Aims and Predictions

Our research group has previously reported that despite considerable improvement across a 2-year period, girls and boys with ADHD remained impaired regarding ADHD symptoms, internalizing behaviors, and EFs relative to typically developing (TD) children (Skogli et al., 2014). There was no effect of gender on ADHD symptoms, EFs test results, or on internalizing behaviors across time. In our earlier study (Skogli, Teicher, Andersen, Hovik, & Øie, 2013), we found a self-report/parent rating discrepancy regarding internalizing symptoms at baseline examination. Self-reporting has been shown to be informative regarding internalizing problems in the girls with ADHD (Skogli et al., 2013). Only internalizing behaviors reported by the parents were reported in our earlier 2-year follow-up study (Skogli et al., 2014). Most of the other longitudinal studies on children with ADHD have used behavior rating scales and checklists completed by teachers and parents; few have included self-report of depression symptoms. Parents are not the most reliable reporters of depression symptoms in their children, and they generally report fewer symptoms than their children (Angold et al., 1987). It has been documented that children 8 years and older are reliable reporters of their internal mood states (Frigerio, Pesenti, Molteni, Snider, & Battaglia, 2001). A persuasive argument has been made for clinicians to pay attention to reports by both parents and children (Shin, Cho, Lim, & Cho, 2008). In the current study, we therefore aimed to extend our investigation of children with ADHD (Skogli et al., 2014) to include self-reported depression symptoms in the longitudinal analyses of gender differences. Furthermore, in the current study, we wanted to conduct new separate analyses correlating parent-reported depression symptoms and child-reported depression symptoms. As the parent-rated Internalizing Composite score used in Skogli et al.’s (2014) article includes symptoms of anxiety, and the measure of depression symptoms completed by the child participants (Short Mood and Feelings Questionnaire [SMFQ]) is a measure of depression symptoms, we used the Withdrawn/Depressed subscale instead of the Internalizing Composite score from the Child Behavior Checklist/6-18 (CBCL; Achenbach & Rescorla, 2001). As far as we know, no studies have investigated whether changes in ADHD symptoms and EFs are associated with changes in parent-rated depression symptoms and in self-rated symptoms of depression in girls and boys with ADHD. We also wanted to use hierarchical regression analyses to make stronger conclusions regarding causal relationships. Furthermore, few earlier studies have included both boys and girls with ADHD in the same study, which precluded direct comparisons of boys and girls (Rinsky & Hinshaw, 2011). A greater understanding of ADHD in females compared with boys, especially its longitudinal course, is a continuing research priority (Hinshaw et al., 2006). It is important for both clinical practice and researchers to better understand the associations among psychopathological symptoms and EFs in boys and girls with ADHD. This may support and advance the development of interventions for this vulnerable group of children.

Based on previous research findings (e.g., Roy et al., 2014), it was predicted that girls with ADHD would have more self-rated symptoms of depression than boys with ADHD. Based on our own and other research, we expected a modest correlation between parent- and self-reported depression symptoms. Furthermore, we expected to find that a reduction in ADHD symptoms was associated with a reduction in both self-reported and parent-rated depression symptoms in girls with ADHD. Finally, we expected that a maturation of inhibition would be associated with a reduction in self/parent-rated depression symptoms in boys and that maturation of working memory and planning ability would be associated with a reduction of self/parent-rated symptoms of depression in girls with ADHD.

Method

Procedure

Seventy-five children with ADHD and 47 TD children between 9 and 16 years of age participated in the study. The participants were recruited as consecutive referrals for assessment and treatment of possible ADHD or other neurodevelopmental disorders at Centers for Child and Adolescent Mental Health in two neighboring Norwegian counties (Hedmark and Oppland). Demographic characteristics are presented in Table 1. The age span in this part of the project with focus on development has been restricted to 9 to 16 years instead of 8 to 17 to ensure greater age homogeneity. All participants underwent a comprehensive assessment according to common clinical practice. Semi-structured clinical interviews (Kiddie-Schedule for Affective Disorders and Schizophrenia [Kiddie-SADS]; Kaufman et al., 1997) were conducted separately for children/adolescents and parents to assess psychopathology. The interviewers were psychologists and educational therapists highly experienced in assessment and treatment of ADHD. Validity and reliability have been reported as good to excellent for Kiddie-SADS with test–retest reliability ranging from .63 to 1.00 and interrater reliability ranging from 93% to 100% (Kaufman et al., 1997; Kim et al., 2004). The diagnostic evaluation with Kiddie-SADS was supplemented with information from the ADHD Rating Scale–IV (ARS-IV; DuPaul, 1998) and the CBCL (Achenbach & Rescorla, 2001), which covers the Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR; American Psychiatric Association, 2000) criteria for ADHD symptoms. Teacher reports (narrative descriptions or Teacher’s Report Form from the Achenbach System of Empirically Based Assessment 1991) describing both academic and social school functioning are mandatory on referral and were incorporated into the diagnostic evaluation. Diagnoses were considered positive, if, based on a comprehensive evaluation of Kiddie-SADS, and the teacher information and the rating scales, DSM-IV-TR (American Psychiatric Association, 2000) criteria were met. The results from the Kiddie-SADS interview and supporting information from rating scales were then reviewed independently by the supervising senior clinician who is a specialized psychologist in neurodevelopmental disorders. Disagreements were discussed in meetings with all the clinicians present to arrive at a “best-estimate” DSM-IV-TR consensus diagnosis (American Psychiatric Association, 2000). Procedures for reassessment at follow-up (T2) were the same as for baseline (T1).

Table 1.

Demographic Characteristics: Means and Standard Deviations by Group and Assessment Time.

	Baseline (T1)				Follow-up (T2)
	ADHD		TDC		ADHD		TDC
	Boys (n = 39)	Girls (n = 36)	Boys (n = 29)	Girls (n = 18)	Boys (n = 39)	Girls (n = 36)	Boys (n = 29)	Girls (n = 18)
Age (years)	11.2 (1.9)	12.0 (2.0)	11.4 (1.9)	11.6 (1.9)	13.2 (2.0)	14.1 (2.1)	13.5 (1.4)	13.9 (2.1)
Time since T1 (months)	—	—	—	—	24.1 (3.7)	24.8 (1.8)^a	25.0 (1.7)	24.6 (3.4)
Mother’s education (years)	12.5 (2.4)	13.1 (1.8)	14.7 (2.5)	14.6 (2.1)
FSIQ^a	94.5 (13.5)	96.4 (15.7)	102.5 (13.0)	107.1 (13.1)	97.0 (15.3)	93.1 (14.0)	105.2 (13.7)	108.7 (11.0)

Note. TDC = typically developing children.

FSIQ = Full-Scale IQ (Wechsler Abbreviated Scale of Intelligence).

Exclusion criteria for all participants included prematurity (<36 weeks), IQ below 70, a history of stimulant treatment, or any disease affecting the central nervous system. All TD children were screened for mental disorders in separate Kiddie-SADS interviews for children/adolescents and parents. The TD children were recruited from local schools and were given a small compensation for participating. TD children were also screened in interviews (child and parent/s separately) for any psychiatric condition fulfilling DSM-IV-TR criteria, as well as head injuries involving loss of consciousness or known dyslexia. See Skogli et al. (2013) for detailed recruitment strategy and diagnostic measures. The study was approved by the Regional Committees for Medical Research Ethics in Eastern Norway (REK-Øst) and by the Privacy protection ombudsman for research at Innlandet Hospital Trust. The study was conducted in accordance with the Helsinki Declaration of the World Medical Association General Assembly.

Participants at Baseline Assessment (T1)

Seventy-eight participants with ADHD participated in the baseline assessment (T1). Three boys with ADHD refused to participate at T2, however. Only the 75 participants with ADHD available for reassessment at T2 (96% of the original cohort) were included in the current study. At baseline (T1), 39 males with ADHD (M = 11.2 years), 36 females with ADHD (M = 12.0 years), 29 TD males (M = 11.4 years), and 18 TD females (M = 11.9 years) between 9 and 16 years of age were included. The four groups (ADHD/males, ADHD/females, TD/males, and TD/females) did not differ significantly with regard to age and gender distribution. The groups differed significantly with regard to IQ (Wechsler Abbreviated Scale of Intelligence; Wechsler, 1999), F(3, 118) = 4.36, p = .006, η_p² = .10. Bonferroni corrected post hoc analyses showed that boys in the ADHD group scored significantly below TD females. On average, mothers of children in the TD group had 1.8 years more education than mothers of children with ADHD, F(3, 118) = 7.01, p < .001. However, the education level of the mothers of the children in the TD group was nearly equal to that of mothers of TD children in other studies in Norway (Heiervang, Mednick, Sundet, & Rund, 2010). None of the participants were prescribed psychopharmaca at T1.

Participants at 2-Year Follow-Up Assessment (T2)

A follow-up assessment (T2) was conducted approximately 24 months following baseline assessment. The same procedure (Kiddie-SADS and all the rating scales) was followed in both assessments. In four cases where the participants were unable to meet at the clinic for reassessment, telephone interviews were performed with the parents/caregivers. Of the 75 participants with ADHD reassessed at T2, two boys and two girls were rated with ADHD symptoms below cutoff and did not receive an ADHD diagnosis. There were no significant differences in age and IQ (p > .05) between the children with ADHD available for reassessment and those three lost to follow-up. Due to fatigue or refusal to perform some of the tests or rating scales, a complete reassessment was not possible in all cases. All TD children were available for reassessment at T2 (n = 47), and none of the participants (ADHD and TD) were excluded at T2 due to neurological or somatic illnesses known to influence cognitive function. The participants with ADHD and TD children did not differ significantly with regard to age and gender distribution at T2 (p < .05).

After inclusion at T1, participants in the ADHD group received standard psychological and/or medical treatment for ADHD-related problems. At T2, a majority of the participants with ADHD had completed their clinical treatment and were no longer patients at Innlandet Hospital Trust. The participants receiving stimulant medication at T2 (24 boys and 18 girls; Equasym, Concerta, and Ritalin) were tested after medication was discontinued for at least 24 hr before reassessment. One female participant forgot to discontinue stimulant medication prior to testing at T2. One boy with ADHD was prescribed Zoloft (10 mg) at T2.

Measures of EF

See Skogli and colleagues (2013) for detailed descriptions of EF measures.

Working memory: The Letter–Number Sequencing Test (LN; a subtest from the Wechsler Intelligence Scale for Children–Fourth Edition; Wechsler, 2004). In the present study, total correct recalled trials were examined. Lower raw scores indicated difficulties with the task.

Inhibition: The Color–Word Interference Test, Condition 3 (CW3; Delis, Kaplan, & Kramer, 2001; Stroop, 1935). For the present study, completion time in seconds was examined. Higher raw scores indicated difficulties with the task.

Mental flexibility: The Color–Word Interference Test, Condition 4 (CW4; Delis et al., 2001; Stroop, 1935). For the present study, completion time in seconds was examined. Higher raw scores indicated difficulties with the task.

Measures of Core ADHD Symptoms

The assessment of core ADHD symptoms was evaluated with the ARS-IV filled out by the parents (DuPaul, Power, Anastoupolous, & Reid, 1998). The psychometric properties of the scale have been investigated in a multinational study of 600 children and adolescents with ADHD (Zhang, Faries, Vowles, & Michelson, 2005). The test–retest reliability of the ARS-IV ranges from .77 to .89. The internal consistency of the scale has also been found to be satisfactory (Cronbach’s α = .80; Zhang et al., 2005).

Measures of Depression Symptoms

Parent-rated depression symptoms

We used the total score from the Withdrawn/Depressed narrow-band subscale from the CBCL (Achenbach & Rescorla, 2001) to measure parent-rated depression symptoms. This subscale has been shown to have adequate internal consistency (Cronbach’s α = .84) and test–retest reliability (Achenbach & Rescorla, 2001). It discriminates between youths with major depressive disorder or dysthymia from youths without these diagnoses (Ebesutani et al., 2010). The CBCL is a broad-spectrum inventory that records, in standardized format, the behavioral and emotional problems and competencies of children aged 4 to 18, as reported by their parents or parent surrogates. It is a widely used scale containing seven competence items and 113 specific problem items. Parents rate the items on a 3-point Likert-type scale with the values: 0 = not true, 1 = somewhat or sometimes true, 2 = very often true. The 120 items assess adaptive behavior as well as eight narrow-band factors and two broadband factors (Externalizing and Internalizing symptoms) of coexisting symptoms during the last 6 months. Elevated T-scores indicate a higher degree of depression symptoms. Cross-cultural studies of the CBCL have demonstrated good discriminant validity with mean factor loadings across societies at .62 (Ivanova et al., 2007). Acceptable reliability and validity of the Norwegian version of the CBCL are reported by Nøvik (1999, 2000). Findings from research support the utility of the CBCL in identifying patterns of comorbidities within the context of ADHD (Biederman, Monuteaux, Kendrick, Klein, & Faraone, 2005).

Self-rated depression symptoms

The SMFQ (Angold et al., 1995) is a 13-item self-report instrument designed to measure depression symptoms in children 8 to 18 years of age. It is derived from the original 30-item Mood and Feelings Questionnaire (Costello & Angold, 1988), where children respond on a 3-point scale (not true, sometimes true, and true). A net score was generated based on the 13 items with elevated raw scores indicating a higher degree of depression symptoms. The SMFQ has demonstrated high internal consistency (Cronbach’s α = .90; Costello, Benjamin, Angold, & Silver, 1991) and test–retest stability in children over a 2-week period (an intraclass correlation of .66; Costello & Angold, 1988). The SMFQ has been found to correlate strongly with the Children’s Depression Inventory (CDI; Kovacs, 1983) and the Diagnostic Interview Schedule for Children (DISC) depression scores (Costello & Angold, 1988; r = .67 and .51, respectively).

Data Analyses

Data analyses were conducted using the statistical package SPSS for Windows, version 21.0 (IBM, SPSS, Inc., Chicago, Illinois). Demographic characteristics were investigated using the one-way ANOVA (continuous variables). Mixed between–within participant ANOVAs (mixed ANOVA) were conducted for each dependent variable to estimate the effect of group (ADHD vs. TD children) and gender on EFs performance across time, followed up by Fisher’s least significant difference (LSD) test for group comparisons.

Change scores were computed by subtracting raw scores at T2 from T1 when high raw scores indicated difficulties with the task; change scores were computed by subtracting raw scores at T1 from T2 when low raw scores indicated difficulties with the task. Raw score data from the EF tests were used due to greater variability in responses than standardized scores.

Hierarchical multiple regression analyses were performed to determine the association between changes in symptoms of depression, ADHD symptoms, and EFs. Separate analyses were performed to examine changes in self- and parent-reported symptoms using depression as a dependent variable. Blocks of predictors were entered into the models in five steps. In the baseline model (Model 1), gender and age were entered as independent variables and thus served as control variables in all subsequent analyses. In Model 2, we added the two core ADHD variables: changes in symptoms hyperactivity/impulsivity and inattention. Model 3 tested for gender-moderation in these symptoms. In Model 4, we added the three measures of changes in EFs. Finally, in Model 5, we tested for possible gender-moderation effects influencing EFs. The increase in explained variance (R²) was assessed for each block. Significant results are reported at p < .05 and p < .01 levels.

Results

Means and standard deviations of ADHD symptoms, depression symptoms, and EFs at T1 and T2 are presented in Table 2. The longitudinal course of self-reported depression symptoms from the SMFQ revealed a significant interaction effect of Group × Gender, F(1, 111) = 4.15, p = .044, η_p² = .036. Separate mixed ANOVAs conducted for the ADHD and TD children groups revealed a significant effect of gender in the ADHD group, with girls displaying significantly more depression symptoms than boys on the SMFQ, F(1, 66) = 8.21, p = .006, η_p² = .11. There was no effect of time on the SMFQ, F(1, 111) = 0.77, p = .383, η_p² = .01. The results are presented in Table 3.

Table 2.

Means and Standard Deviations of ADHD Symptoms, Depression Symptoms, and Executive Functions at T1 and T2 in Girls and Boys With ADHD and TDC.

	Baseline (T1)				Follow-up (T2)
	ADHD		TDC		ADHD		TDC
	Boys (n = 39)	Girls (n = 36)	Boys (n = 29)	Girls (n = 18)	Boys (n = 39)	Girls (n = 36)	Boys (n = 29)	Girls (n = 18)
Inattention symptoms^a	17.1 (5.7)	15.2 (5.7)	1.6 (1.9)	1.4 (1.6)	13.3 (6.7)	10.5 (5.9)	2.0 (2.2)	0.9 (1.3)
Hyperactivity/impulsivity symptoms^a	10.6 (6.6)	9.8 (6.8)	1.0 (1.3)	0.8 (1.4)	8.5 (7.2)	6.0 (5.7)	0.7 (1.3)	0.3 (0.5)
Withdrawn/depressed^b	59.2 (6.8)	58.7 (7.3)	51.4 (2.6)	51.2 (2.6)	57.3 (7.0)	57.3 (7.0)	50.9 (1.8)	50.2 (0.9)
Depression symptoms^c	5.8 (4.7)	7.8 (5.2)	2.4 (2.7)	1.9 (1.6)	4.4 (4.5)	7.8 (5.0)	1.6 (1.6)	2.6 (2.0)
Working memory^d	15.3 (3.7)	16.2 (2.5)	18.2 (1.9)	18.8 (1.5)	17.2 (2.7)	17.5 (2.8)	19.9 (2.1)	19.2 (1.9)
Inhibition^e	89.2 (28.0)	83.4 (31.6)	74.8 (20.7)	63.1 (16.6)	72.4 (25.1)	69.4 (28.2)	59.4 (16.6)	53.4 (14.3)
Mental flexibility^f	128.4 (47.1)	113.3 (46.0)	103.8 (34.5)	93.2 (37.3)	98.8 (34.6)	92.9 (43.4)	80.3 (28.4)	70.7 (25.0)

Note. TDC = typically developing children; CBCL = Child Behavior Checklist/6-18; SMFQ = Short Mood and Feelings Questionnaire.

ADHD Rating Scale–IV, raw scores.

The CBCL, T-scores. Higher scores denote greater pathology on CBCL. T-scores of 65 and above are considered to represent clinically significant areas of concern.

SMFQ, raw score. Higher scores denote greater pathology.

The Letter–Number Sequencing Test, number-correct raw score.

The Color–Word Interference Test, Condition 3, time in seconds, raw score.

The Color-Word Interference Test, Condition 4, time in seconds, raw score.

Table 3.

Symptom Change: Means and Standard Deviations by Group and Assessment Time.

Variable	ADHD (n = 75)		TDC (n = 47)		Group		Time		Group × Time		Group × Gender		Group × Time × Gender
Variable	T1	T2	T1	T2	F	p	F	p	F	p	F	p	F	p
Attention symptoms ^a	16.2 (5.8)	12.0 (6.5)	1.5 (1.8)	1.6 (2.0)	(1, 116) 289.2	<.001	(1, 116) 14.4	<.001	(1, 116) 14.0	<.001	(1, 116) 1.5	ns	(1, 116) 0.0	ns
Hyperactivity/impulsivity symptoms ^b	10.2 (6.7)	7.3 (6.6)	1.0 (1.3)	0.6 (1.1)	(1, 116) 91.0	<.001	(1, 116) 10.2	.002	(1, 116) 5.7	.019	(1, 116) 0.6	ns	(1, 116) 0.5	ns
Withdrawn/depressed ^c	58.9 (7.0)	57.3 (6.9)	51.1 (2.6)	50.6 (1.5)	(1, 117) 60.21	<.001	(1, 117) 5.48	.02	(1, 117) 0.94	ns	(1, 117) 0.026	ns	(1, 117) 0.107	ns
Depression Symptoms ^d	6.8 (5.0)	6.1 (5.0)	2.2 (2.3)	1.9 (1.8)	(1, 111) 52.1	<.001	(1, 111) 0.8	ns	(1, 111) 0.4	ns	(1, 111) 4.1	.044	(1, 111) 0.0	ns

Note. Higher scores denote greater pathology on the ADHD Rating Scale–IV, the CBCL, and on the SMFQ. T-scores of 65 and above are considered to represent clinically significant areas of concern on the CBCL. TDC = typically developing children.

a,b

ADHD rating scale – IV, ADHD

The Child Behavior Checklist/6-18 (CBCL)

Short Mood and Feelings Questionnaire (SMFQ).

We conducted independent T tests comparing the children with ADHD taking stimulant medication at T2 with the children with ADHD not taking stimulant medication to investigate any possible influence the medication may have had on symptom reporting at follow-up assessment. There was no significant difference in the two groups for parent-reporting of inattention symptoms, hyperactivity/impulsivity, parent-rated depression symptoms, nor for self-reported depression symptoms.

We observed a modest correlation between self- and parent-reported symptoms of depression at both T1 (r = .30, p < .001) and T2 (r = .26, p < .01), and no significant association in the change in depression symptoms that occurred over the two measurement waves (r = .025, p = .76).

Results from the two hierarchical regression analyses are presented in Tables 4 and 5. For parent-reported depression symptoms, a significant improvement in model fit relative to the baseline model was observed when ADHD symptoms were added (ΔR² = .19, ΔF = 6.84, p = .002), and again when sex-moderation was included (ΔR² = .09, ΔF = 3.63, p = 0.03). However, subsequent inclusion of EFs as predictors only resulted in marginal and nonsignificant improvement (ΔR² = .05, ΔF = 1.3, p = .29), suggesting that EFs contributed little to explained variability in parent-reported depression symptoms over and above that accounted for by ADHD symptoms. Consequently, Model 3 was selected as having the overall best fit. Of the predictors included in this model, only sex-moderated inattention was found to be significant, suggesting that a reduction in inattention was associated with a decrease in parent-reported depression symptoms in girls (p = .015). In Model 3, 28% of the variance was explained.

Table 4.

Summary of Hierarchical Regression Analysis for Changes in Self-Reported Depression Symptoms.

Variable	Model 1	Model 2	Model 3	Model 4	Model 5
Constant	−8.208	−8.292	−7.538 [−16.52, 1.45]	−9.218	−9.395
Age	0.85*	0.93*	0.83* [0.05, 1.61]	0.90*	0.89*
Gender	−2.24	−2.27	−1.05 [−4.46, 2.36]	−0.93	−0.37
ChgAtt		−0.23*	−0.33* [−0.61, −0.05]	−0.33*	−0.34*
ChgHyper		0.04	0.36* [0.04, 0.68]	0.31	0.30
ChgAtt × Gender			0.16 [−0.26, 0.57]	0.18	0.17
ChgHyper × Gender			−0.59** [−1.02, −0.16]	−0.55*	−0.56*
ChgWM				0.20	0.19
ChgInhib				0.03	0.02
ChgMentFlex				0.01	0.02
ChgWM × Gender					−0.04
ChgInhib × Gender					0.03
ChgMentFlex × Gender					−0.03
R ²	0.09	0.16	0.27	0.29	0.30
F	2.74	2.63*	3.22**	2.27*	1.71
ΔR²		0.07	0.11	0.02	0.01
ΔF		2.38	3.85**	0.54	0.31

Note. The table displays the unstandardized regression coefficients for the five models, with the 95% confidence intervals given for the best fitting model. ChgAtt = change score Attention Symptoms, ADHD Rating Scale–IV; ChgHyper = change score Hyperactivity/Impulsivity, ADHD Rating Scale–IV; ChgWM = change score Working Memory, the Letter–Number Sequencing Test (a subtest from the Wechsler Intelligence Scale for Children–Fourth Edition); ChgInhib = change score Inhibition, the Color–Word Interference Test, Condition 3; ChgMentFlex = change score Mental Flexibility, the Color–Word Interference Test, Condition 4.

p < .05. **p < .01.

Table 5.

Summary of Hierarchical Regression Analysis for Changes in Parent-Reported Depression Symptoms.

Variable	Model 1	Model 2	Model 3	Model 4	Model 5
Constant	2.12	0.89	0.77 [−8.73, 10.27]	2.74	2.76
Age	0.01	−0.02	0.07 [−0.75, 0.88]	−0.08	−0.10
Gender	−0.99	−1.21	−3.62 [−7.28, 0.04]	−3.34	−2.81
ChgAtt		0.39*	0.15 [−0.16, 0.45]	0.13	0.15
ChgHyper		0.02	0.04 [−0.32, 0.40]	0.01	0.00
ChgAtt × Gender			0.57* [0.12, 1.03]	0.55*	0.54*
ChgHyper × Gender			−0.02 [−0.50, 0.45]	−0.04	0.01
ChgWM				0.44	0.44
ChgInhib				−0.01	0.02
ChgMentFlex				−0.03	−0.03
ChgWM × Gender					−0.10
ChgInhib × Gender					−0.08
ChgMentFlex × Gender					0.03
R ²	0.005	0.190	0.28	0.33	0.34
F	0.163	3.52*	3.76**	2.96**	2.23*
ΔR²		0.19	0.09	0.05	0.01
ΔF		6.84**	3.63*	1.27	0.36

p < .05. **p < .01.

For self-reported depression symptoms, Model 3 was again found to be the best fit. Adding ADHD symptoms to the baseline model did not significantly improve fit (ΔR² = .07, ΔF = 2.38, p = .10). Allowing these to be moderated by sex resulted in a significant improvement (ΔR² = .11, ΔF = 3.85, p = .03). Subsequent inclusion of EFs in Model 4 only resulted in a marginal and nonsignificant improvement (ΔR² = .02, ΔF = 0.54, p = .66), and there was no evidence of sex-moderation on EFs (ΔR² = .01, ΔF = .31, p = .82).

Model 3 could account for 27% of the variance in self-reported depression symptoms. In both girls and boys, controlling for age, sex, and hyperactivity/impulsivity, a reduction in inattention was associated with an increase in self-reported depression symptoms. For hyperactivity/impulsivity, the pattern of effects was different across genders. In boys, a reduction in hyperactivity was associated with a significant decrease in self-reported depression, while in girls, it was associated with a significant increase.

Discussion

In our previous research, we found considerable improvement across a 2-year period in a clinical sample of both girls and boys with ADHD regarding parent-rated internalizing behaviors (Skogli et al., 2014). However, when we extended our analyses in the current study to include self-rated symptoms of depression, we found in accordance with our predictions a significant effect of gender in the ADHD group. Girls with ADHD displayed significantly more self-rated depression symptoms than ADHD boys after 2 years. This is in line with other studies showing that adolescent females with ADHD report more internalizing symptoms than their male counterparts (Roy et al., 2014). However, the gender difference was only apparent in self-rated depression symptoms in our ADHD group, and only at follow-up. Furthermore, we found as expected only a modest correlation between self-reported and parent-reported depression at both T1 and T2. There was no significant agreement between parents’ report and the child’s self-report regarding the change in depression symptoms that occurred over the follow-up period. During the 2-year follow-up period, the children with ADHD in our study received treatment-as-usual. A possibility is that treatment improved core ADHD symptoms but not symptoms of depression in the girls with ADHD and that the parents interpreted the improved core ADHD symptoms as reduced depression symptoms. However, the high degree of self-perceived symptoms of depression in the girls did not change. Another possibility is that the parents are less aware of how their children feel because of situational factors such as mental state and level of stress that influence parents’ accounts of their children’s problems and/or that the children exaggerate when they report depression symptoms (Berg-Nielsen, Vika, & Dahl, 2003). Our findings support the conclusion of previous authors that it is important that clinicians pay attention to reports by both parents and children regarding symptoms of depression, especially in girls, otherwise the symptoms of depression may go unrecognized and untreated (Shin et al., 2008).

The lack of change in self-reported symptoms of depression from baseline to follow-up for girls with ADHD contradicts findings reported by Lahey et al. (2007), which suggest that symptoms of depression and anxiety typically increase in early adolescence among children with ADHD. The absence of an increase in self-reported symptoms of depression may be an indication of possible treatment effect during the 2-year period. However, the results may also indicate that girls with ADHD demonstrate greater stability than boys with ADHD in comorbid psychopathology from childhood into adolescence (Monuteaux et al., 2010).

In the current study, we also wanted to investigate the relationship between changes in self-rated symptoms of depression and parent-rated symptoms of depression, core ADHD symptoms, and EFs over a 2-year period in girls with ADHD compared with boys with ADHD. As predicted, the results indicated that ADHD inattention symptoms were associated with a decline in parent-rated depression symptoms in girls with ADHD. In a population-based cohort of individuals followed up from birth to 20 years of age, teacher- and self-reported peer rejection and popularity mediated the pathways from ADHD symptoms to depression symptoms (Humphreys et al., 2013). Exploratory analyses of gender differences showed that dislike and victimization mediated the paths to depression in girls but not in boys. This finding could be explained on the basis of girls’ higher sensitivity to peer opinions (Bakker et al., 2010). In our study, we did not have any measures of peer rejection or popularity. A hypothesis based on the results may be that the association between a reduction in ADHD inattention symptoms and a reduction in depression symptoms as perceived by the parents may have been mediated through higher sensitivity to peer opinions and popularity in girls. Research has revealed that peers are more likely to be tolerant of higher levels of attention deficit disorder (ADD) symptoms among boys than girls (Diamantopoulou, Henricsson, & Rydell, 2005). Thus, when attention symptoms decrease, the girls with ADHD may be more tolerated by their peers, and their parents may perceive their daughters to be less depressed.

Consistent with our prediction, a reduction in symptoms of hyperactivity/impulsivity was associated with a decrease in self-rated depression symptoms in boys with ADHD. However, in contrast to our expectations, a reduction in symptoms of hyperactivity/impulsivity was associated with increased self-rated depression symptoms in girls with ADHD. It has also been speculated that females with ADHD may develop better coping strategies than males with ADHD and, as a result, can better mask their ADHD symptoms (Quinn, 2008). Thus, the girls with ADHD may develop better coping strategies for the “overt” core symptoms of impulsivity/hyperactivity and depression symptoms observed by the parents, but the symptoms may still be apparent and increase “inside” the girls. Thus, a strategy developed to cope with overt hyperactivity/impulsive symptoms may be related to increased self-perceived depression symptoms. Impulsive behaviors have been conceptualized as behavioral attempts to alleviate negative emotions (Verdejo-Garcia, Rivas-Peresz, Vilar-Lopez, & Perez-Garcia, 2007). Thus, impulsive behaviors may serve as a maladaptive emotion regulation strategy. If the girls with ADHD inhibit impulsive behavior, but have no other adaptive emotion regulation strategy, self-perceived symptoms of depression may increase. Another hypothesis may be that the girls are more popular and attract more attention from peers when they exhibit hyperactive/impulsive behavior. When these symptoms decrease, they may feel less popular resulting in increased symptoms of depression.

In contrast to our predictions, a reduction of inattention symptoms in both girls and boys was associated with an increase in self-reported depression symptoms. It is possible that when the symptoms of attention decrease, the children have more opportunity to speculate about their situation and how they feel, which results in an increase in symptoms of depression.

Another unexpected finding was that changes in EFs contributed little to the explained variability of changes in depression symptoms. However, deficits in EFs have been found to be strongly associated with ADHD symptoms (Willcutt et al., 2005). When we in our analyses controlled for the impact changes in ADHD symptoms had on changes in symptoms of depression, the changes in EFs were not able to explain the changes in depression symptoms uniquely. Consequently, our interpretation is thus that the lack of a significant contribution of EFs was mainly due to the fact that we controlled for the impact changes in ADHD symptoms were having on depression symptoms.

Strengths and Limitations of the Study

A longitudinal design with few dropouts (4%) constitutes a major strength of this study. Another strength is that the girls and boys with ADHD did not differ regarding age, IQ, or reported levels of inattention and hyperactivity/impulsivity symptoms. Furthermore, our study included both parent-rated depression symptoms and self-rated assessments of symptoms of depression.

Limitations of the study are that the group of children with ADHD was restricted to clinic-referred children and not representative of the ADHD population in general. The large age span (9-16 years at T1) might represent a limitation, but small standard deviations in age reflect the fact that most participants were around mean age at T1 (M = 11.5, SD = 2.0). Age was also entered as an independent variable in the hierarchical multiple regression analyses and thus served as a control variable in all subsequent analyses. Although we were able to control for the effect of stimulant treatment, we did not have the possibility to control for type and duration of psychological intervention between T1 and T2.

Conclusion

According to our 2-year follow-up study of clinic-referred girls and boys with ADHD, self-rated depression symptoms remained at a high level in girls with ADHD. A reduction in hyperactivity/impulsivity was associated with a reduction in self-rated depression symptoms in boys, and an increase in girls. A reduction in inattention symptoms was associated with a modest increase in self-rated depression symptoms in both genders. After controlling for ADHD symptoms, executive functioning was not found to be significantly associated with either self- or parent-reported depression symptoms. Collecting information from both parents and the child with ADHD is important in determining how gender influences factors involved in determining the development of emotional well-being in these children. Our results may have implications for practitioners of clinical child psychology. An awareness that a reduction in symptoms of hyperactivity/impulsivity is closely associated with an increase in self-perceived symptoms of depression in girls is highly relevant when treating girls with ADHD.

Footnotes

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: The project has received financial support from Innlandet Hospital Trust (grant number 150186) and the Regional Resource Center for Autism, ADHD, Tourette syndrome and Narcolepsy, Oslo University Hospital (grant number 150182).

Author Biographies

Merete Øie, PhD, is professor at the Department of Psychology at the University of Oslo, and a research adviser at the Innlandet Hospital Trust, Norway. Her research interests include neuropsychological functions in ADHD and other neuropsychiatric disorders.

Kjell Tore Hovik, PhD, is a clinical psychologist at Innlandet Hospital Trust, Division Mental Health Care, Norway. His research focuses on the regulation of cognition, emotion, and behavior in children and adolescents with Tourette’s Syndrome, ADHD, and Autistic Spectrum Disorders.

Per Normann Andersen, PhD, is associate professor at Lillehammer University College, Faculty of Education and Social Work, Norway. His research focuses on the regulation of cognition, emotion, and behavior in children and adolescents with Tourette’s Syndrome, ADHD, and Autistic Spectrum Disorders.

Nikolai Olavi Czajkowski, PhD, is associate professor at the University of Oslo and holds a position at the Norwegian Institute of Public Health. His research is primarily focused on the genetic epidemiology of mental disorders.

Erik Winther Skogli, PhD, is a clinical psychologist at Innlandet Hospital Trust, Division of Habilitation and Rehabilitation, Norway. His research focuses on the regulation of cognition, emotion, and behavior in children and adolescents with Tourette’s Syndrome, ADHD, and Autistic Spectrum Disorders.

References

Achenbach

T. M.

Rescorla

L. A.

(2001). Manual for the ASEBA school-age forms & profiles. Burlington: Research Center for Children, Youth, and Families, University of Vermont.

American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., text rev.). Washington, DC: Author.

Anderson

(2002). Assessment and development of executive function (EF) during childhood. Child Neuropsychology, 8, 71-82.

Angold

Costello

E. J.

Messer

S. C.

Pickles

Winder

Silver

(1995). Development of a short questionnaire for use in epidemiological studies of depression in children and adolescents. International Journal of Methods in Psychiatric Research, 5, 1-12.

Angold

Weissman

M. M.

John

Merikangas

K. R.

Prusoff

B. A.

Wickramaratne

. . . Warner

(1987). Parent and child reports of depressive symptoms in children at low and high risk of depression. Journal of Child Psychology and Psychiatry, 28, 901-915.

Bakker

M. P.

Ormel

Verhulst

F. C.

Oldehinkel

A. J.

(2010). Peer stressors and gender differences in adolescents’ mental health: The TRAILS study. The Journal of Adolescents Health, 46, 444-450.

Bauermeister

J. J.

Shrout

P. E.

Chavez

Rubio-Stipec

Ramirez

Padilla

. . . Canino

(2007). ADHD and gender: Are risks and sequela of ADHD the same for boys and girls? Journal of Child Psychology and Psychiatry, 48, 831-839.

Becker

Roessner

Breuer

Döpfner

Rothenberger

(2011). Relationship between quality of life and psychopathological profile: Data from an observational study in children with ADHD. European Child & Adolescent Psychiatry, 20(Suppl. 2), S267-S275.

Berg-Nielsen

T. S.

Vika

Dahl

A. A.

(2003). When adolescents disagree with their mothers: CBCL-YSR discrepancies related to maternal depression and adolescent self-esteem. Child: Care, Health and Development, 29, 207-213.

10.

Biederman

Kwon

Aleardi

Chouinard

V. A.

Marino

Cole

. . . Faraone

S. V.

(2005). Absence of gender effects on attention deficit hyperactivity disorder: Findings in nonreferred subjects. American Journal of Psychiatry, 162, 1083-1089.

11.

Biederman

Monuteaux

M. C.

Kendrick

Klein

K. L.

Faraone

S. V.

(2005). The CBCL as a screen for psychiatric comorbidity in paediatric patients with ADHD. Archives of Disease in Childhood, 90, 1010-1015.

12.

Biederman

Petty

C. R.

O’Connor

K. B.

Hyde

L. L.

Faraone

S. V.

(2012). Predictors of persistence in girls with attention deficit hyperactivity disorder: Results from an 11-year controlled follow-up study. Acta Psychiatrica Scandinavica, 125, 147-156.

13.

Costello

E. J.

Angold

(1988). Scales to assess child and adolescent depression: Checklists, screens, and nets. Journal of the American Academy of Child & Adolescent Psychiatry, 27, 726-737.

14.

Costello

E. J.

Benjamin

Angold

Silver

(1991). Mood variability in adolescents: A study of depressed, nondepressed and comorbid patients. Journal of Affective Disorders, 23, 199-212.

15.

de Boo

G. M.

Prins

P. J.

(2007). Social incompetence in children with ADHD: Possible moderators and mediators in social-skills training. Clinical Psychology Review, 27, 78-97.

16.

Delis

Kaplan

Kramer

(2001). Delis-Kaplan Executive Function System (D-KEFS) (Norwegian version). Stockholm, Sweden: Pearson Assessment.

17.

Diamantopoulou

Henricsson

Rydell

(2005). ADHD symptoms and peer relations of children in a community sample: Examining associated problems, self-perceptions, and gender differences. International Journal of Behavioral Development, 5, 388-398.

18.

Diamond

(2013). Executive functions. Annual Review of Psychology, 64, 135-168.

19.

DuPaul

G. J.

Power

T. J.

Anastoupolous

A. D.

Reid

(1998). ADHD Rating Scale–IV: Checklists, norms, and clinical interpretation. New York, NY: Guilford Press.

20.

Ebesutani

Bernstein

Nakamura

Chorpita

Higa-McMillan

Weisz

(2010). Concurrent validity of the Child Behavior Checklist DSM-oriented scales: Correspondence with DSM diagnoses and comparison to syndrome scales. Journal of Psychopathology and Behavioral Assessment, 32, 373-384.

21.

Elkins

I. J.

Malone

Keyes

Iacono

W. G.

McGue

(2011). The impact of attention-deficit/hyperactivity disorder on preadolescent adjustment may be greater for girls than for boys. Journal of Clinical Child & Adolescent Psychology, 40, 532-545.

22.

Fontaine

Carbonneau

Barker

E. D.

Vitaro

Hébert

Côté

S. M.

. . . Tremblay

R. E.

(2008). Girls’ hyperactivity and physical aggression during childhood and adjustment problems in early adulthood: A 15-year longitudinal study. Archives of General Psychiatry, 65, 320-328.

23.

Frigerio

Pesenti

Molteni

Snider

Battaglia

(2001). Depressive symptoms as measured by the CDI in a population of northern Italian children. European Psychiatry, 16, 33-37.

24.

Gogtay

Giedd

J. N.

Lusk

Hayas

K. M.

Greenstein

Vaituzis

A. C.

. . . Thompson

P. M.

(2004). Dynamic mapping of human cortical development during childhood through early adulthood. Proceedings of the National Academy of Sciences of the United States of America, 101, 8174-8179.

25.

Heiervang

K. S.

Mednick

Sundet

Rund

B. R.

(2010). The Chernobyl accident and cognitive functioning: A study of Norwegian adolescents exposed in utero. Developmental Neuropsychology, 35, 643-655.

26.

Hinshaw

S. P.

Owens

E. B.

Sami

Fargeon

(2006). Prospective follow-up of girls with attention-deficit/hyperactivity disorder into adolescence: Evidence for continuing cross-domain impairment. Journal of Consulting and Clinical Psychology, 74, 489-499.

27.

Hinshaw

S. P.

Owens

E. B.

Zalecki

Huggins

S. P.

Montenegro-Nevado

A. J.

Schrodek

Swanson

E. N.

(2012). Prospective follow-up of girls with attention-deficit/hyperactivity disorder into early adulthood: Continuing impairment includes elevated risk for suicide attempts and self-injury. Journal of Consulting and Clinical Psychology, 80, 1041-1051.

28.

Humphreys

K. L.

Katz

S. J.

Lee

S. S.

Hammen

Brennan

P. A.

Najman

J. M.

(2013). The association of ADHD and depression: Mediation by peer problems and parent–child difficulties in two complementary samples. Journal of Abnormal Psychology, 122, 854-867.

29.

Ivanova

M. Y.

Dobrean

Dopfner

Erol

Fombonne

Fonseca

A. C.

. . . Chen

W. J.

(2007). Testing the 8-syndrome structure of the Child Behavior Checklist in 30 societies. Journal of Clinical Child and Adolescent Psychology, 36, 405-417.

30.

Kaufman

Birmaher

Brent

Rao

Flynn

Moreci

. . . Ryan

(1997). Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (K-SADS-PL): Initial reliability and validity data. Journal of the American Academy of Child & Adolescent Psychiatry, 36, 980-988.

31.

Kim

Y. S.

Cheon

K. A.

Kim

B. N.

Chang

S. A.

Yoo

H. J.

Kim

J. W.

. . . Leventhal

(2004). The reliability and validity of Kiddie-Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version-Korean version (K-SADS-PL-K). Yonsei Medical Journal, 45, 81-89.

32.

Kovacs

(1983). The Children’s Depression Inventory: A self-rated depression scale for school-aged youngsters. Pittsburgh, PA: University of Pittsburgh School of Medicine.

33.

Lahey

B. B.

Hartung

C. M.

Loney

Pelham

W. E.

Chronis

A. M.

Lee

S. S.

. . . Tannock

(2007). Are there sex differences in the predictive validity of DSM-IV ADHD among younger children? Journal of Clinical Child & Adolescent Psychology, 36, 113-126.

34.

Miyake

Friedman

N. P.

Emerson

M. J.

Witzki

A. H.

Howerter

Wager

T. D.

(2000). The unity and diversity of executive functions and their contributions to complex ‘‘frontal lobe’’ tasks: A latent variable analysis. Cognitive Psychology, 41, 49-100.

35.

Monuteaux

M. C.

Faraone

Gross

L. M.

Biederman

(2007). Predictors, clinical characteristics, and outcome of conduct disorder in girls with attention-deficit/hyperactivity disorder: A longitudinal study. Psychological Medicine, 37, 1731-1741.

36.

Monuteaux

M. C.

Mick

Faraone

S. V.

Biederman

(2010). The influence of sex on the course and psychiatric correlates of ADHD from childhood to adolescence: A longitudinal study. Journal of Child Psychology and Psychiatry, 51, 233-241.

37.

Nøvik

T. S.

(1999). Validity of the Child Behaviour Checklist in a Norwegian sample. European Child & Adolescent Psychiatry, 8, 247-254.

38.

Nøvik

T. S.

(2000). Child Behavior Checklist item scores in Norwegian children. European Child & Adolescent Psychiatry, 9, 54-60.

39.

Nøvik

T. S.

Hervas

Ralston

S. J.

Dalsgaard

Rodrigues

P. R.

Lorenzo

M. J.

ADORE Study Group. (2006). Influence of gender on attention-deficit/hyperactivity disorder in Europe—ADORE. European Child & Adolescent Psychiatry, 1, 15-24.

40.

Nussbaum

N. L.

(2012). ADHD and female specific concerns: A review of the literature and clinical implications. Journal of Attention Disorders, 16, 87-100.

41.

Pingault

J. B.

Viding

Galéra

Greven

C. U.

Zheng

Plomin

Rijsdijk

(2015). Genetic and environmental influences on the developmental course of attention-deficit/hyperactivity disorder symptoms from childhood to adolescence. JAMA Psychiatry, 72, 651-658.

42.

Quinn

P. O.

(2008). Attention-deficit/hyperactivity disorder and its comorbidities in women and girls: An evolving picture. Current Psychiatry Reports, 10, 419-423.

43.

Riggs

N. R.

Blair

C. B.

Greenberg

M. T.

(2003). Concurrent and 2-year longitudinal relations between executive function and the behavior of 1st and 2nd grade children. Child Neuropsychology, 9, 267-276.

44.

Riggs

N. R.

Greenberg

M. T.

Kusche

C. A.

Pentz

M. A.

(2006). The mediational role of neurocognition in the behavioral outcomes of a social-emotional prevention program in elementary school students: Effects of the PATHS curriculum. Prevention Science, 7, 91-102.

45.

Rinsky

J. R.

Hinshaw

S. P.

(2011). Linkages between childhood executive functioning and adolescent social functioning and psychopathology in girls with ADHD. Child Neuropsychology, 17, 368-390.

46.

Roy

Hartman

C. A.

Veenstra

Oldehinkel

A. J.

(2015). Peer dislike and victimisation in pathways from ADHD symptoms to depression. European Child & Adolescent Psychiatry, 24, 887-895.

47.

Roy

Oldehinkel

A. J.

Verhulst

F. C.

Ormel

Hartman

C. A.

(2014). Anxiety and disruptive behavior mediate pathways from attention-deficit/hyperactivity disorder to depression. The Journal of Clinical Psychiatry, 75, 108-113.

48.

Rucklidge

J. J.

(2010). Gender differences in attention-deficit/hyperactivity disorder. The Psychiatric Clinics of North America, 33, 357-373.

49.

Seidman

L. J.

(2006). Neuropsychological functioning in people with ADHD across the lifespan. Clinical Psychology Review, 26, 466-485.

50.

Seidman

L. J.

Biederman

Monuteaux

M. C.

Valera

Doyle

A. E.

Faraone

S. V.

(2005). Impact of gender and age on executive functioning: Do girls and boys with and without attention deficit hyperactivity disorder differ neuropsychologically in preteen and teenage years? Developmental Neuropsychology, 27, 79-105.

51.

Seymour

K. E.

Chronis-Tuscano

Iwamoto

D. K.

Kurdziel

Macpherson

(2014). Emotion regulation mediates the association between ADHD and depressive symptoms in a community sample of youth. Journal of Abnormal Child Psychology, 42, 611-621.

52.

Shin

Y. M.

Cho

Lim

K. Y.

Cho

S. M.

(2008). Predictors of self-reported depression in Korean children 9 to 12 years of age. Yonsei Medical Journal, 49, 37-45.

53.

Skogli

E. W.

Andersen

P. N.

Hovik

K. T.

Øie

(2014). Development of hot and cold executive function in boys and girls with ADHD: A 2-year longitudinal study. Journal of Attention Disorders. Advance online publication. doi:10.1177/1087054714524984 (accessed 13 March 2014).

54.

Skogli

E. W.

Teicher

M. H.

Andersen

P. N.

Hovik

K. T.

Øie

(2013). ADHD in girls and boys—Gender differences in co-existing symptoms and executive function measures. BMC Psychiatry, 13, Article 298. doi:10.1186/1471-244X-13-298

55.

Snyder

H. R.

(2013). Major depressive disorder is associated with broad impairments on neuropsychological measures of executive function: A meta-analysis and review. Psychological Bulletin, 139, 81-132.

56.

Stroop

J. R.

(1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18, 643-662.

57.

Verdejo-Garcia

Rivas-Peresz

Vilar-Lopez

Perez-Garcia

(2007). Strategic self-regulation, decision-making and emotion processing in poly-substance abusers in their first year of abstinence. Drug and Alcohol Dependence, 86, 139-146.

58.

Walcott

C. M.

Landau

(2004). The relation between disinhibition and emotion regulation in boys with attention deficit hyperactivity disorder. Journal of Clinical Child & Adolescent Psychology, 4, 772-782.

59.

Wechsler

(1999). Wechsler Abbreviated Scale of Intelligence (Norwegian version). Stockholm, Sweden: The Psychological Corporation.

60.

Wechsler

(2004). Wechsler Intelligence Scale for Children–Fourth edition (Norwegian version). Stockholm, Sweden: The Psychological Corporation.

61.

Willcutt

E. G.

Doyle

A. E.

Nigg

J. T.

Faraone

S. V.

Pennington

B. F.

(2005). Validity of the executive function theory of attention-deficit/hyperactivity disorder: A meta-analytic review. Biological Psychiatry, 57, 1336-1346.

62.

Yap

M. B.

Allen

N. B.

O’Shea

di Parsia

Simmons

J. G.

Sheeber

(2011). Early adolescents’ temperament, emotion regulation during mother-child interactions, and depressive symptomatology. Development and Psychopathology, 23, 267-282.

63.

Zhang

Faries

D. E.

Vowles

Michelson

(2005). ADHD Rating Scale IV: Psychometric properties from a multinational study as a clinician-administered instrument. International Journal of Methods in Psychiatric Research, 14, 186-201.