Comorbidity in hyperactive children: issues related to selection bias, gender, severity, and internalizing symptoms

Childhood conduct problems and young adult outcomes among women with childhood attention-deficit/hyperactivity disorder (ADHD)

We tested whether conduct problems predicted young adult functioning and psychiatric symptoms among women diagnosed with attention-deficit/hyperactivity disorder (ADHD) during childhood, in the context of 3 potential adolescent mediators: internalizing problems, peer rejection, and school failure and disciplinary problems. We controlled for childhood ADHD severity, IQ, and demographic factors, and in the mediational tests, for adolescent conduct problems. Data came from 140 participants in the Berkeley Girls With ADHD Longitudinal Study. We used bootstrapping methods to assess indirect effects (mediators). Both childhood, F(1, 118) change = 9.00, p = .003, R2 change = .069, and adolescent, F(1, 109) change = 10.41, p = .002, R2 change = .083, conduct problems were associated with worse overall functioning during young adulthood, controlling for initial ADHD severity, child IQ, and demographics. Results were similar when predicting psychiatric symptoms. Adolescent school failure and disciplinary problems mediated the relations between childhood conduct problems and both young adult functioning and externalizing problems; adolescent internalizing problems and peer conflict mediated the relation between childhood conduct problems and young adult internalizing problems. As is true for boys, childhood and adolescent conduct problems are associated with poor adult outcomes among girls with ADHD, with school failure and disciplinary problems, internalizing problems, and peer conflict functioning as mediators of these relations.

Comorbid externalising behaviour in AD/HD: evidence for a distinct pathological entity in adolescence

While the profiling of subtypes of Attention Deficit Hyperactivity Disorder (AD/HD) have been the subject of considerable scrutiny, both psychometrically and psychophysiologically, little attention has been paid to the effect of diagnoses comorbid with AD/HD on such profiles. This is despite the greater than 80% prevalence of comorbidity under the DSM-IV-TR diagnostic definitions. Here we investigate the event related potential (ERP) and psychometric profiles of Controls, AD/HD, and comorbid AD/HD (particularly AD/HD+ODD/CD) groups on six neurocognitive tasks thought to probe the constructs of selective and sustained attention, response inhibition and executive function. Data from 29 parameters extracted from a child group (age range 6 to 12; 52 Controls and 64 AD/HD) and from an adolescent group (age range 13 to 17; 79 Controls and 88 AD/HD) were reduced via a Principal Components Analysis, the 6 significant eigenvectors then used as determinants of cluster membership via a Two-Step Cluster Analysis. Two clusters were found in the analysis of the adolescent age group - a cluster dominated by Control and AD/HD participants without comorbidity, while the second cluster was dominated by AD/HD participants with externalising comorbidity (largely oppositional defiant/conduct disorder ODD/CD). A similar segregation within the child age group was not found. Further analysis of these objectively determined clusters in terms of their clinical diagnoses indicates a significant effect of ODD/CD comorbidity on a concurrent AD/HD diagnosis. We conclude that comorbid externalising behaviour in AD/HD constitutes a distinct pathological entity in adolescence.

Genetic and Environmental Influences on the Associations Between Attention Problems and Other Problem Behaviors

Problem behavior in children shows a high degree of cooccurrence, both within the domains of internalizing and externalizing behaviors and across domains. Maternal ratings of 207 same- and opposite-sex twin pairs on the Child Behavior Checklist (CBCL/4–18; Achenbach, 1991) were used to determine the etiology of these associations. In the current sample of 4- to 11-year-old children (mean age: 7.6 years) phenotypic correlations were .68 between Internalizing and Externalizing, between .41 and .66 within the internalizing scales, and between .58 and .71 within the externalizing scales. Correlations across domains on the scale level were of similar magnitude. Genetic and shared environmental correlations were generally high, with the exception of the somatic complaints scale which showed low genetic correlations with other scales. These findings of uniformly high shared etiology was seen within and across domains. For example, Attention Problems showed genetic correlations of .65 with Delinquent Behavior and .76 with Aggressive Behavior; the genetic correlations of Attention Problems with internalizing scales were .71 for Anxious/Depressed and .79 for Withdrawn; a low genetic correlation was only shown for the Somatic Complaints scale (rg = .16). Although the magnitude of shared environmental contributions was lower, the environmental correlations were close to unity, indicating that the same family environmental factors were involved in aspects of problem behavior when assessed across domains. Results for the Attention Problems scale were similar to other disruptive behavior, justifying its inclusion with the externalizing scales.

Pure Versus Co-occurring Externalizing and Internalizing Symptoms in Children: The Potential Role of Socio-Developmental Milestones

Co-occurring internalizing and externalizing disorders are moderately prevalent in children, adolescents, and adults (Anderson, Williams, McGee, & Silva, 1987; McConaughy & Skiba, 1994), but much remains to be understood regarding why some children show "pure" versus co-occurring internalizing and externalizing symptoms. One possible influence that has previously not been considered is the failure to attain socio-developmental milestones, which paradoxically may prevent the development of co-occurring symptoms for some children. The present study proposes a model in which failure to attain relevant socio-developmental milestones might explain why some children may not develop heterotypic co-occurring symptoms. Specifically, it is proposed that specific clusters of internalizing symptoms (i.e., high social anxiety, withdrawal, and inhibition) and externalizing symptoms (i.e., high impulsivity, hyperactivity, and emotional reactivity) may be associated with the failure to attain socio-developmental milestones (i.e., poor peer relations for anxious children, lack of self-reflection and evaluation for impulsive/reactive children) that, in turn, may prevent subgroups of children from developing co-occurring, heterotypic symptoms.

Gender differences in ADHD subtype comorbidity

OBJECTIVE

To examine gender differences in attention-deficit/hyperactivity disorder ("ADHD") symptom comorbidity with "oppositional defiant disorder", "conduct disorder", "separation anxiety disorder", "generalized anxiety disorder", speech therapy, and remedial reading in children.

METHOD

From 1994 to 1995, data from a large sample (N = 4,371) of twins and siblings studied in the Australian Twin ADHD Project were obtained by mailed DSM-IV-based questionnaires, investigating patterns of comorbidity in the three subtypes of "ADHD": "inattentive", "hyperactive/impulsive", and "combined". A total of 1,550 questionnaires were returned (87%) over the next 12 to 18 months.

RESULTS

Analysis of variance showed significant between-group differences in males and females for inattention and hyperactive/impulsive symptom counts with higher rates of "oppositional defiant disorder" and "conduct disorder" in males, and higher rates of "separation anxiety disorder" in females indicating internalizing disorders are more common in females and externalizing disorders are occurring more often in males. Differences were found between the "ADHD" subtypes and the no ADHD category for all comorbid conditions, for both males and females. Children without ADHD consistently had fewer symptoms, while children with the combined subtype showed consistently more comorbid symptoms indicating a strong relationship between high rates of externalizing symptoms and high rates of internalizing symptoms. Gender differences in speech therapy were significant only for the children without ADHD. The rates of "separation anxiety disorder" were higher in females with the "inattention" subtype and the rate of "generalized anxiety disorder" higher for females with the "combined" subtype, indicating that the subtypes of ADHD were associated with these internalizing disorders in different ways.

CONCLUSIONS

Although comorbidity differs among ADHD subtypes, there were no significant gender differences in comorbidity for externalizing disorders. Inattentive girls may present with anxiety. Clinical approaches for both males and females should be sensitive to possible language and reading problems.

Correlates of comorbid psychopathology in children with ADHD

OBJECTIVE

To investigate correlates of internalizing and externalizing psychopathology in a clinical sample of children with attention-deficit/hyperactivity disorder (ADHD).

METHOD

Parent and teacher Child Behavior Checklists were administered to 300 children with ADHD to ascertain comorbid symptoms. Based on previous research, a seven-step hierarchical regression analysis was developed. Six hierarchical regression analyses were conducted with either parent or teacher Child Behavior Checklist aggression, delinquency, or anxious/depressive comorbid symptoms as dependent measures.

RESULTS

Controlling for (1) variables known to increase risk for ADHD child psychopathology and (2) estimated duration of ADHD, our results suggest that the presence of comorbid symptoms is influenced by age of onset. An early age of onset of ADHD was correlated with a greater rate of parent-reported child aggressive symptoms, and a later age of onset was correlated with a greater rate of parent-reported child anxious/depressive symptoms. Elevated levels of comorbid externalizing and internalizing symptoms are associated with greater ADHD symptom severity.

CONCLUSIONS

Comorbid externalizing and internalizing symptoms are correlated with age of ADHD onset and are related to the severity of clinical presentation in a referred sample of children with ADHD.

Rates and patterns of comorbidity of adolescent behavioral syndromes as reported by parents and teachers in a Taiwanese nonreferred sample

OBJECTIVE

To evaluate the rates and patterns of comorbidity between behavioral syndromes in adolescents as reported by parents and teachers. Whether the patterns of comorbidity were "epiphenomenal" was also assessed.

METHOD

Parents of 854 randomly selected students (response rate = 88%) in Taipei in 1996 completed the Child Behavior Checklist; among them, 240 also were randomly selected to have the Teacher's Report Form completed by their teachers. In addition to bidirectional comorbidity rates, odds ratios with and without other comorbid pairs controlled for were estimated via multiple logistic regressions.

RESULTS

High comorbidity rates between behavioral syndromes were found in adolescents as reported both by parents and teachers except for that of Somatic Complaints with other syndromes. When other comorbidity pairs were controlled for, the comorbidity rates between Anxious/Depressed with externalizing syndromes turned out to be epiphenomenal, whereas those between externalizing syndromes remained high for both informants' reports. Attention Problems also remained significantly comorbid with other syndromes in the multiple logistic regressions except for that of Aggressive Behavior in the Teacher's Report Form sample.

CONCLUSION

High comorbidity rates between adolescent behavioral syndromes exist in both parents' and teachers' reports, and it is important to control for the epiphenomenal condition when assessing such comorbidity rates.