Background: To examine the comorbidity of ADHD in association with family environment and the severity of ADHD.
Method: A screening for ADHD symptoms was conducted among adolescents in the Northern Finland 1986 Birth Cohort (N = 6622). A sample of those adolescents (n = 457), aged 16-18 years, with and without ADHD symptoms was assessed with a diagnostic interview (Kiddie-SADS-PL) and ADHD and comorbid disorders were studied in association with the family characteristics and the number of ADHD symptoms.
Results: Adolescents with ADHD had more commonly conduct disorder (P < 0.001), oppositional defiant disorder (P < 0.001), substance abuse (P < 0.001) and mild depression (P < 0.001) than adolescents without ADHD. Adolescents with ADHD and comorbid disorders had more ADHD symptoms (P < 0.001) than those with ADHD alone. Compared to adolescents with ADHD alone those with ADHD and comorbidity lived significantly more commonly in non-intact families, in low-income families, with mothers who were dissatisfied with life and with parents who showed little interest in their adolescents' activities.
Conclusions: Adolescents who develop externalizing disorders comorbid to ADHD seem to suffer from a severe form of ADHD and live in family environments that may not provide sufficient support for optimal development of an adolescent with ADHD.