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.     

Functional consequences of attention‐deficit hyperactivity disorder on children and their families

Attention‐deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder with core symptoms that include hyperactivity, impulsiveness, and inattention, and it is the most common psychiatric disorder among children and adolescents. These core symptoms are continuously recognized throughout the day from childhood to adulthood. Furthermore, children with ADHD from childhood to adulthood might also have various comorbid psychiatric disorders. Recently, bipolar disorder and disruptive mood dysregulation disorder, a new clinical issue, have been discussed as comorbid disorders or differential disorders associated with ADHD. Furthermore, comorbid disorders of ADHD are related to quality of life and family burden. Children with ADHD have poorer long‐term outcomes than controls with respect to: academic achievement and attainment, occupational rank and job performance, risky sexual practices and early unwanted pregnancies, substance use, relationship difficulties, marital problems, traffic violations, and car accidents. Irritability of children with ADHD has been a key symptom that clinicians and researchers have used to evaluate the developmental condition of children with ADHD. ADHD is sometimes a chronic disorder that occurs over a long period, increasing the family burden of these children (including health‐care costs), which will increase with aging for unremitted children with ADHD. Therefore, clinicians should evaluate not only the mental condition of the child but also the family burden. Children with ADHD should be treated during childhood to reduce their clinical symptoms and family burden.     

What can ADHD without comorbidity teach us about comorbidity?

Neuropsychiatric comorbidity in ADHD is frequent, impairing and poorly understood. In this report, characteristics of comorbid and comorbid-free ADHD subjects are investigated in an attempt to identify differences that could potentially advance our understanding of risk factors.In a clinically-referred ADHD cohort of 449 youths (ages 6-18), age, gender, IQ, SES and ADHD symptoms were compared among ADHD comorbid free subjects and ADHD with internalizing and externalizing disorders. Logistic regression analyses were also carried out to investigate the relationship between comorbidity and parental psychiatric status.Age range was younger in the ADHD without comorbidity and older in ADHD + internalizing disorders. No significant difference in IQ or SES was found among ADHD comorbid and comorbid-free groups. ADHD with internalizing disorder has a significantly greater association with paternal psychiatric conditions. After matching by age, gender, IQ and SES, ADHD with externalizing disorders had significantly higher total ADHD, hyperactivity/impulsivity score and single item score of difficulty awaiting turn than ADHD without comorbidity and ADHD with internalizing disorders.Older age ranges, ADHD symptom severity and parental psychopathology may be risk factors for comorbidity.     

Psychiatric disorders and behavioral characteristics of pediatric patients with both epilepsy and attention-deficit hyperactivity disorder

OBJECTIVE: Attention-deficit hyperactivity disorder (ADHD) coexisting with epilepsy is poorly understood; thus, we compared the clinical correlates and psychiatric comorbid conditions of 36 children with epilepsy and ADHD aged 6 to 17 years enrolled in an ADHD treatment trial, with those reported in the literature on children with ADHD without epilepsy. METHODS: Measures included the Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children (KSADS), the Wechsler Abbreviated Scale of Intelligence (WASI), and the Scales for Independent Behavior-Revised (SIB-R). RESULTS: Mean IQ was 86+/-19, and SIB-R Standard Score was 72+/-26. The ADHD-Combined subtype, composed of both inattentive and hyperactive symptoms, was most frequent (58%). Sixty-one percent exhibited a comorbid disorder, including anxiety disorders (36%) and oppositional defiant disorder (31%). CONCLUSIONS: Comorbidity in ADHD with epilepsy is similar to that in ADHD without epilepsy reported in the literature. These preliminary data argue that the pathophysiology of ADHD has common components in both populations.     

Child temperament,ADHD, and caregiver strain: exploring relationships in an epidemiological sample

OBJECTIVE: To investigate the relationship between child-reported dimensions of temperament and attention-deficit/ hyperactivity disorder (ADHD), as well as other indicators of child psychopathology, including disruptive disorders, depression, and anxiety. It also examined whether difficult child temperament scores independently predicted caregiver strain. METHOD: A school-district-wide, two-phase screening design (response rate 70% for phase 2) identified elementary school children at high risk for ADHD. Two hundred high-risk children and their parents completed standardized instruments to assess child temperament, diagnoses of disruptive disorders, children's symptoms of anxiety and depression, and caregiver strain. Relationships were examined using analysis of variance, correlations, and multivariate prediction models, adjusting for child sociodemographic characteristics and psychopathology. All estimates were weighted for sampling design and differential participation. RESULTS: Combined subtype ADHD was associated with lower scores on task orientation and higher scores on general activity level. Depressive symptoms correlated significantly with all but one difficult temperament dimension, in a pattern consistent with clinical symptoms of depression. Child temperament did not vary by ADHD treatment status. Among these high-risk children, maternal caregiver strain experiences were increased by male gender, inattention symptoms, and oppositional defiant disorder, but not by difficult temperament scores. CONCLUSION: This study provides support for Graham and Stevenson's hypothesis of continuity between specific temperament traits and certain child psychiatric disorders, namely ADHD and depressive disorders.     

Prospective, longitudinal study of tic, obsessive-compulsive, and attention-deficit/hyperactivity disorders in an epidemiological sample

OBJECTIVE: Understanding the interrelatedness of tics, obsessive-compulsive disorder (OCD), and attention-deficit/hyperactivity disorder (ADHD) has been complicated by studying only cross-sectional samples of clinically referred subjects. The authors report the cross-sectional and longitudinal associations of these disorders in an epidemiological sample of children followed prospectively into early adulthood. METHOD: Structured diagnostic interview information was acquired on 976 children, aged 1 to 10 years, who were randomly selected from families living in upstate New York in 1975. Reassessments were acquired in 776 of these subjects 8, 10, and 15 years later. Diagnostic prevalences were estimated at each time point. The associations among tics, OCD, and ADHD were assessed within and across time points, as were their associations with comorbid illnesses and demographic risk factors. RESULTS: In temporal cross-section, tics and ADHD symptoms were associated with OCD symptoms in late adolescence and early adulthood after demographic features and comorbid psychiatric symptoms were controlled. In prospective analyses, tics in childhood and early adolescence predicted an increase in OCD symptoms in late adolescence and early adulthood. ADHD symptoms in adolescence predicted more OCD symptoms in early adulthood, and OCD in adolescence predicted more ADHD symptoms in adulthood. The associations of tics with ADHD were unimpressive in temporal cross-section and were not significant in prospective analyses. Tics, OCD, and ADHD shared numerous complex associations with demographic and psychopathological risk factors. ADHD was associated with lower IQ and lower social status, whereas OCD was associated with higher IQ. CONCLUSIONS: Tics and OCD were significantly associated in this sample, as were OCD and ADHD. These findings are in general consistent with those from family studies, and they help to define the natural history, comorbid illnesses, and interrelatedness of these conditions.     

Comorbid anxiety and depression in school-aged children with attention deficit hyperactivity disorder (ADHD) and selfreported symptoms of ADHD,anxiety, and depression among parents of school-aged children with and without ADHD

Background

Attention deficit hyperactivity disorder (ADHD) is a common psychiatric disorder in children that can extend into adulthood and that is often associated with a variety of comorbid psychiatric disorders.

Aim

Assess the comorbidity of ADHD with anxiety disorders and depressive disorders in school-aged children, and the relationship of the severity of ADHD, anxiety, and depressive symptoms in children who have ADHD with the severity of the corresponding symptoms in their parents.

Methods

A two-stage screening process identified children 7-10 years of age with and without ADHD treated at the Xin Hua Hospital in Shanghai. ADHD and other DSM-IV diagnoses were determined by a senior clinician using the Schedule for Affective Disorder and Schizophrenia for School-Aged Children (K-SADS-PL). One parent for each enrolled child completed three self-report scales: the ADHD Adult Self Report Scale (ASRS), the State-Trait Anxiety Inventory (STAI), and the Beck Depression Inventory (BDI). In total 135 children with ADHD and 65 control group children without ADHD were enrolled; parents for 94 of the children with ADHD and 63 of the children without ADHD completed the parental assessment scales.

Results

Among the 135 children with ADHD, 27% had a comorbid anxiety disorder, 18% had a comorbid depressive disorder, and another 15% had both comorbid anxiety and depressive disorders. Parents of children with ADHD self-reported more severe ADHD inattention symptoms than parents of children without ADHD and were more likely to meet criteria for adult ADHD. Mothers (but not fathers) of children with ADHD had significantly more severe trait anxiety and depressive symptoms than mothers of children without ADHD. Among children with ADHD, the severity of ADHD symptoms was not significantly correlated with the severity of ADHD symptoms in parents, but depressive symptoms and anxiety symptoms in the children were significantly correlated with the corresponding symptoms in the parents.

Conclusion

School-aged children with ADHD commonly suffer from comorbid anxiety and depressive disorders, and the severity of these symptoms parallels the level of anxiety and depressive symptoms in their parents. Self-reported symptoms of ADHD are significantly more common in parents of children with ADHD than in parents of children without ADHD. Longitudinal studies are needed to disentangle the genetic, biological, and social factors responsible for these complex inter-relationships.     

Treatment of attention deficit hyperactivity disorder in children

Objective The present study investigated the predictive power of anxiety, IQ, severity of ADHD and parental depression on the outcome of treatment in children with ADHD. Method Fifty children with ADHD (ages 8–12) were randomized to a 10-week treatment of methylphenidate or to a treatment of methylphenidate combined with multimodal behavior therapy. Prior to treatment predictors were assessed. Outcome was assessed separately for parents and teachers on a composite measure of inattentive, hyperactive, oppositional- and conduct disorder symptoms. Results There was neither a significant difference between the two treatments at baseline nor did treatment condition predict outcome. Therefore the data were collapsed across the two treatments. A combination of anxiety and IQ predicted teacher-rated outcome, explaining 18% of the variance. Higher anxiety and higher IQ’s indicated better treatment outcome. There were no significant predictors of the parent-rated outcome. Conclusion This study showed a small but significant predictive effect of IQ and anxiety on treatment outcome in children with ADHD. Clinical implications This study supports the idea that for the treatment of ADHD children with comorbid anxiety and higher IQ respond better to the two most used treatments for ADHD.     

Does maternal ADHD reduce the effectiveness of parent training for preschool children's ADHD?

OBJECTIVE: To assess the impact of maternal attention-deficit/hyperactivity disorder (ADHD) symptoms on the effectiveness of a parent training (PT) program for preschool ADHD. METHOD: Eighty-three 3-year-old children with ADHD and their mothers selected from two community cohorts living in Hampshire, England (1992-93 and 1995-96, respectively), completed an 8-week PT program. ADHD symptoms and a number of other parent and child factors, including adult ADHD symptoms, were measured prior to the start of treatment (week 1: T1), immediately after treatment (week 8: T2), and at 15 weeks follow-up (week 23: T3). RESULTS: Mothers were divided into three groups on the basis of their scores (T1) on the Adult AD/HD Rating Scale (high, medium, low). Children of mothers in the high-ADHD group displayed no improvement after PT, whereas the levels of ADHD symptoms of the children of mothers in either the medium or low ADHD groups reduced substantially (F(4,60) = 3.13, p < .05). This association persisted after other child and maternal factors were controlled for in multiple regression analyses (beta > .30, p < .05). CONCLUSIONS: High levels of maternal ADHD symptoms limit the improvement shown by children with ADHD after a program of PT. This effect was unrelated to other aspects of maternal mental health and child functioning. The treatment of parental ADHD may be a prerequisite for the success of psychosocial interventions for childhood ADHD.     

Attention-deficit/hyperactivity disorder and dissociative disorder among abused children

The aim of this study was to investigate the psychiatric problems and characteristics among children of child abuse (CA). Specifically, the authors investigated whether attention-deficit/hyperactivity disorder (ADHD) symptoms were exhibited before or after CA. A total of 39 abused child inpatients who were treated at Aichi Children's Health and Medical Center, Aichi, Japan, (mean age, 10.7 +/- 2.6; mean IQ scores, 84.1 +/- 19.3) were included in the study. The most frequent diagnosis was dissociative disorder in 59% of abused subjects. ADHD was diagnosed in 18% of abused subjects, and 71% of ADHD children had comorbid dissociative disorder. A total of 67% of all CA subjects fulfilled the ADHD criteria A according to DSM-IV-TR, however, only 27% of those fulfilled the criteria before CA. The subjects of dissociative disorder fulfilled ADHD criteria A more frequently than those of non-dissociative disorder (P = 0.013), and this result led to an increase in the frequency of the apparent ADHD. The rate of ADHD-suspected parents in the subjects who fulfilled ADHD criteria A after CA was significantly lower than those who fulfilled it before CA (P = 0.005). While it is difficult to distinguish ADHD from dissociative disorder, abused children may have increased apparent ADHD due to dissociative disorder. Further studies should be conducted in order to explore the distinct biological differences between ADHD before CA and the subjects who fulfilled ADHD criteria A after CA.     

Comorbid Depressive Disorders in ADHD: The Role of ADHD Severity,Subtypes and Familial Psychiatric Disorders

Objective

To evaluate the presence of Major Depressive Disorder (MDD) and Dysthymic Disorder (DD) in a sample of Italian children with Attention Deficit Hyperactivity Disorder (ADHD) and to explore specific features of comorbid depressive disorders in ADHD.

Methods

Three hundred and sixty-six consecutive, drug-naïve Caucasian Italian outpatients with ADHD were recruited and comorbid disorders were evaluated using DSM-IV-TR criteria. To evaluate ADHD severity, parents of all children filled out the ADHD Rating Scale. Thirty-seven children with comorbid MDD or DD were compared with 118 children with comorbid conduct disorder and 122 without comorbidity for age, sex, IQ level, family psychiatric history, and ADHD subtypes and severity.

Results

42 of the ADHD children displayed comorbid depressive disorders: 16 exhibited MDD, 21 DD, and 5 both MDD and DD. The frequency of hyperactive-impulsive subtypes was significantly lower in ADHD children with depressive disorders, than in those without any comorbidity. ADHD children with depressive disorders showed a higher number of familial psychiatric disorders and higher score in the Inattentive scale of the ADHD Rating Scale, than children without any comorbidity. No differences were found for age, sex and IQ level between the three groups.

Conclusion

Consistent with previous studies in other countries, depressive disorders affect a significant proportion of ADHD children in Italy. Patient assessment and subsequent treatment should take into consideration the possible presence of this comorbidity, which could specifically increase the severity of ADHD attention problems.     

Psychological distress in children with developmental coordination disorder and attention-deficit hyperactivity disorder

This study explored whether or not a population-based sample of children with developmental coordination disorder (DCD), with and without comorbid attention deficit/hyperactivity disorder (ADHD), experienced higher levels of psychological distress than their peers. A two-stage procedure was used to identify 244 children: 68 with DCD only, 54 with ADHD only, 31 with comorbid DCD and ADHD, and 91 randomly selected typically developing (TD) children. Symptoms of depression and anxiety were measured by child and parent report. Child sex and caregiver ethnicity differed across groups, with a higher ratio of boys to girls in the ADHD only group and a slightly higher proportion of non-Caucasian caregivers in the TD group. After controlling for age, sex, and caregiver ethnicity, there was significant variation across groups in both anxiety (by parent report, F(3,235) = 8.9, p < 0.001; by child report, F(3,236) = 5.6, p = 0.001) and depression (parent report, F(3,236) = 23.7, p < 0.001; child report, F(3,238) = 9.9, p < 0.001). In general, children in all three disorder groups had significantly higher levels of symptoms than TD children, but most pairwise differences among those three groups were not significant. The one exception was the higher level of depressive symptoms noted by parent report in the ADHD/DCD group. In conclusion, children identified on the basis of motor coordination problems through a population-based screen showed significantly more symptoms of depression and anxiety than typically developing children. Children who have both DCD and ADHD are particularly at heightened risk of psychological distress.     

Co-Occurring Posttraumatic Stress Disorder and Depression Among Young Children

The purpose of this study was to examine differences in: (1) mental health emotional and behavioral problems between young children experiencing PTSD with and without MDD; (2) the incidence of caregiver PTSD and MDD between children with PTSD?±?MDD; and (3) the number of traumatic events and interpersonal versus non-interpersonal nature of trauma events among children whose parents sought child trauma-focused treatment. Sixty-six caregivers of children aged 3–7 with PTSD completed semi-structured interviews regarding caregiver and child diagnoses, and caregivers completed self-report measures regarding child symptomatology. Results indicated that young children with PTSD?+?MDD had significantly higher internalizing symptoms, dissociative symptoms, and posttraumatic stress severity than those without comorbid MDD. There were no significant group differences in the incidence of caregiver PTSD or MDD, or the number or types of traumatic events. Future research to understand the unique contributors to the etiology of MDD in the context of PTSD among young children is needed.     

Motor impairment in children with anxiety disorders

This study examined the frequency and degree of motor impairment in referred children with anxiety disorders (AnxDs), compared with children with attention deficit/hyperactivity disorder (ADHD), children with comorbid AnxDs and ADHD, and nonreferred controls. All participants (n=141; 90 males, 51 females; mean age: 10years, 1month; range: 7-13years) had an IQ greater than 70. Diagnoses of mental disorders were established using the Schedule for Affective Disorders and Schizophrenia for School-Aged Children (Kiddie-SADS). Motor ability was assessed using the Movement Assessment Battery for Children (M-ABC). We found that children with AnxDs exhibited significantly higher total impairment scores on the M-ABC than controls, but were not significantly different from children with ADHD or children with comorbid AnxDs and ADHD. All clinical groups exhibited similar profiles of motor impairment. A total of 19 (46%) children with AnxDs scored below the 5th percentile on the M-ABC, indicating that motor function is impaired in many children with AnxDs to a degree that probably interferes with their activities of daily living. These results support the notion that assessment of motor function is important in understanding the daily challenges of children with AnxDs.     

A controlled study of formal thought disorder in children with autism and multiple complex developmental disorders

Along with well-defined categories in classification systems (e.g., autistic disorders and attention-deficit/hyperactivity disorder (ADHD)), practitioners are confronted with many children showing mixed forms of developmental psychopathology. These clusters of symptoms are on the borderlines of more defined categories. The late Donald Cohen proposed heuristic criteria to study a group defined by impaired social sensitivity, impaired regulation of affect, and thinking disorders under the name multiple complex developmental disorders (MCDD). Although these children meet criteria for pervasive developmental disorder--not otherwise specified (PDD-NOS), they have additional important clinical features, such as thought disorder. After highlighting similarities and differences between MCDD and comparable groups (e.g., multidimensionally impaired children), this paper presents the findings of a study comparing formal thought disorder scores in children with MCDD to children with autism spectrum diagnoses, such as autistic disorder (AD), and to children with nonspectrum diagnoses, such as ADHD and anxiety disorders. METHODS: Videotaped speech samples of four groups of high-functioning, latency-aged children with MCDD, AD, ADHD, and anxiety disorders were compared to a control group of normal children using the Kiddie Formal Thought Disorder Rating Scale (K-FTDS). RESULTS: High formal thought disorder scores were found both in the AD and MCDD groups, low rates in the ADHD groups, and no thought disorder in the anxiety disorder and normal control groups. The severity of formal thought disorder was related to verbal IQ scores within the AD and MCDD groups. CONCLUSION: High formal thought scores in children with complex developmental disorders, such as AD and MCDD, appear to reflect impaired communication skills rather than early signs of psychosis.     

Behavioral treatment of swallowing difficulty

Reinforced in vivo practice of a graded sequence of steps was used to treat swallowing difficulty in an adolescent leukemia victim. The patient's medical treatment involved a daily regimen of several pills, and she had from childhood been unable to swallow pills. Practice sessions utilized candy “pills” of various sizes, shapes, and textures. Over ten sessions the number of swallows per trial decreased from 22.5 to 1.1. Follow-up at 5 months, 2 years and 4 years showed no recurrence of swallowing difficulty.     

Current issues and trends in the diagnosis and treatment of adults with ADHD

Attention-deficit/hyperactivity disorder (ADHD) has been commonly thought of as a childhood disorder that diminished over time. It is one of the most common developmental disorders and it is estimated that ADHD affects 5-10% of children. Two-thirds of children with ADHD will continue to have symptoms of ADHD that persist throughout adolescence. Longitudinal studies have demonstrated that symptoms of ADHD can also remain in adulthood, affecting 4.4% of the adult population. However, diagnosing adults with ADHD can prove difficult because they often find that their symptoms are egosyntonic. In addition, the development of comorbid conditions, such as anxiety, depression, personality disorders or substance abuse, can often overshadow underlying ADHD symptoms. Nonetheless, treatments such as stimulant and nonstimulant medication (e.g., atomoxetine), and cognitive-behavior therapy have been effective in treating adults with ADHD. This article reviews the prevalence of adults with ADHD, followed by a discussion of the neurobiological and genetic underpinnings of the disorder. Issues regarding the diagnosis and treatment of ADHD are also addressed.     

Tics and psychiatric comorbidity in children and adolescents

This study examined comorbid psychiatric symptoms in a large, community-based sample of children and adolescents. The study sample comprised a total of 3006 school children: 413 preschool (3 to 5 years; 237 males, 176 females; mean age 4 years 2 months, SD 8 months), 1520 elementary school (5 to 12 years; 787 males, 733 females; mean age 8 years 2 months, SD 1 year 11 months), and 1073 secondary school children (12 to 18 years; 573 males, 500 females; mean age 14 years 4 months, SD 1 year 10 months), all of whom were attending regular education programs. Children were evaluated with a teacher-completed DSM-IV-referenced rating scale. The sample was divided into four groups: attention-deficit-hyperactivity disorder with tics (ADHD+tics), ADHD without tics (ADHD), tics without ADHD (T), and a comparison group i.e. neither ADHD nor tics (Non). The percentage of children with tic behaviors varied with age: preschool children (22.3%), elementary school children (7.8%), and adolescents (3.4%). Tic behaviors were more common in males than females, regardless of comorbid ADHD symptoms. For many psychiatric symptoms, screening prevalence rates were highest for the ADHD groups (ADHD+tics>ADHD>T>Non). However, obsessive-compulsive and simple and social phobia symptoms were more common in the groups with tic behavior. Findings for a community-based sample show many similarities with studies of clinically referred samples suggesting that teacher-completed ratings of DSM-IV symptoms may be a useful methodology for investigating the phenomenology of tic disorders.     

The Comorbidity of Pervasive Developmental Disorder and Attention Deficit Hyperactivity Disorder: Results of a Retrospective Chart Review

Objective: To determine if a sample of children meeting diagnostic criteria for a Pervasive Developmental Disorder (PDD) display symptoms and impairment related to Attention Deficit Hyperactivity Disorder (ADHD) sufficient to warrant a comorbid diagnosis of ADHD. Further, do children with PDD displaying such symptoms demonstrate more impairment in daily life activities than those children only having PDD? Method: A retrospective chart review was conducted on children (N = 57) diagnosed with the PDD's of Autism or PDD-Not Otherwise Specified (PDD-NOS), or ADHD. Comparative analysis of questionnaire and neuropsychological test data was completed to determine the severity of ADHD-like symptoms presenting among children with PDD. Results: From the pool of subjects having PDD with sufficient data (N = 27), 7 or 26% met DSM-IV criteria for the combined type of ADHD. Nine or 33% met diagnostic criteria for the Inattentive Type of ADHD and 11 or 41% did not demonstrate a significant number of ADHD symptoms to warrant a comorbid diagnosis of ADHD. Results indicate that a subgroup of children with PDD displaying significant ADHD-like symptoms may in fact have ADHD thus warranting a comorbid diagnosis of ADHD. Current data did not suggest children with PDD and the combined type of ADHD demonstrated significantly more impairment in daily life functioning than those children only having PDD. However, this appeared likely the result of small sample size. The data, however, does indicate such children experience more difficulties in daily situations as rated by parents and teachers. Conclusion: These findings reinforce clinical observations indicating that some children with PDD may also experience an independent comorbid condition of ADHD, suggesting that a comorbid diagnosis of ADHD with PDD be considered in such cases. If further findings are replicated, the current exclusionary DSM-IV-TR criteria of making such a comorbid diagnosis should be re-considered.     

A Causal and Mediation Analysis of the Comorbidity Between Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD)

Autism spectrum disorder (ASD) and Attention-deficit/hyperactivity disorder (ADHD) are often comorbid. The purpose of this study is to explore the relationships between ASD and ADHD symptoms by applying causal modeling. We used a large phenotypic data set of 417 children with ASD and/or ADHD, 562 affected and unaffected siblings, and 414 controls, to infer a structural equation model using a causal discovery algorithm. Three distinct pathways between ASD and ADHD were identified: (1) from impulsivity to difficulties with understanding social information, (2) from hyperactivity to stereotypic, repetitive behavior, (3) a pairwise pathway between inattention, difficulties with understanding social information, and verbal IQ. These findings may inform future studies on understanding the pathophysiological mechanisms behind the overlap between ASD and ADHD.