Attention-deficit/hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and conduct disorder (CD) are frequently co-occurring disorders in children and adolescents. However, their clinical status among adults is still under discussion. This study analyzes how the current clinical presentation of adult ADHD might be influenced by a lifetime history of CD and ODD.

We compared three groups of patients: ADHD without history of CD/ODD (n = 178), ADHD + history of ODD (n = 184), and ADHD + history of CD (n = 96).

A history of CD (and to a lower extent ODD) is associated with a more severe and externalizing profile.

Past CD and ODD entail a significant negative mental health impact on persistent ADHD, reinforcing the importance of actively assessing the developmental history of adult ADHD patients.

A better understanding of the long-term scope and impact of the co-morbidity with oppositional defiant disorder (ODD) and conduct disorder (CD) in attention deficit hyperactivity disorder (ADHD) youth has important clinical and public health implications.

Subjects were assessed blindly at baseline (mean age=10.7 years), 1-year (mean age=11.9 years), 4-year (mean age=14.7 years) and 10-year follow-up (mean age=21.7 years). The subjects' lifetime diagnostic status of ADHD, ODD and CD by the 4-year follow-up were used to define four groups (Controls, ADHD, ADHD plus ODD, and ADHD plus ODD and CD). Diagnostic outcomes at the 10-year follow-up were considered positive if full criteria were met any time after the 4-year assessment (interval diagnosis). Outcomes were examined using a Kaplan–Meier survival function (persistence of ODD), logistic regression (for binary outcomes) and negative binomial regression (for count outcomes) controlling for age.

ODD persisted in a substantial minority of subjects at the 10-year follow-up. Independent of co-morbid CD, ODD was associated with major depression in the interval between the 4-year and the 10-year follow-up. Although ODD significantly increased the risk for CD and antisocial personality disorder, CD conferred a much larger risk for these outcomes. Furthermore, only CD was associated with significantly increased risk for psychoactive substance use disorders, smoking, and bipolar disorder.

These longitudinal findings support and extend previously reported findings from this sample at the 4-year follow-up indicating that ODD and CD follow a divergent course. They also support previous findings that ODD heralds a compromised outcome for ADHD youth grown up independently of the co-morbidity with CD.