HealthDay News — About one in five children and adolescents with attention-deficit/hyperactivity disorder (ADHD) show signs of autism, study findings indicate.
Kids with ADHD were significantly more likely than those without to have a positive autism trait profile (18% vs. 0.87%; P<0.001), Joseph Biederman, MD, of Massachusetts General Hospital and colleague reported in Pediatrics.
Furthermore, children with both ADHD and autistic traits had significantly more impairment in psychopathology, interpersonal, school, family and cognitive functioning then those who had autistic traits, but not ADHD.
Previous research has suggested the two disorders may have a shared heritability, as autistic traits co-occur in about 20% to 30% of kids with ADHD.
To better understand the relationship between the two, Biederman and colleagues performed a longitudinal, case-control study of patients aged 6 to 18 years attending pediatric medical clinicsat Massachusetts General Hospital. Mean patient age was 11.3 years and nearly all participants were white (99%).
About half required tutoring (61% of those with ADHD and 22% of controls), and about a quarter repeated a grade (25% with ADHD, 7% of controls) or took a special education class (26% with ADHD, 2% of controls).
Participants aged 12 years and older were interviewed using the Kiddie Schedule for Affective Disorders and Schizophrenia-Epidemiologic Version. Parents were interviewed for those aged younger than 12 years. Participants were also evaluated for social withdrawal, social problems, thought problems, anxiety and depression, aggression,social disability, family functioning and intellectual functioning.
A total of 242 children were identified as having ADHD, whereas 227 children and adolescents did not.
The researchers found that autistic traits were significantly more common in those with ADHD (18% versus 0.87%). Those with both ADHD and autistic traits had higher rates of additional ADHD-related symptoms, including clumsiness, hyperactivity and peer fighting compared with those with only ADHD.
Overall, comorbid psychiatric conditions, including disruptive behavior disorders, mood disorders, multiple anxiety disorders, language disorders and substance use disorders were significantly more prevalent in patients with ADHD (P<0.001 for all). Those that also had autistic traits also had higher prevalence on these measures (P<0.001 for all, except P=0.01 for language disorders).
Kids with both ADHD and autistic traits performed significantly worse in school, and on handling activities and problems with peers, siblings and parents.
“A substantial minority of ADHD children manifests autistic traits and those exhibiting autistic traits have greater severity of illness and dysfunction,” the researchers wrote.