Bipolar symptoms in adult attention-deficit/hyperactivity disorder: a cross-sectional study of 510 clinically diagnosed patients and 417 population-based controls.

OBJECTIVE: Bipolar spectrum disorders (BSD) have several symptoms and features in common with attention-deficit/hyperactivity disorder (ADHD). Here we explored the prevalence of BSD and the relationship between symptoms of BSD and ADHD in adult ADHD patients.

METHOD: Norwegian adults diagnosed with DSM-IV ADHD during 1997 through 2007 (n = 510) and a random sample of 417 controls from the general population (aged 18-40 years) were recruited and responded to 85 questions rating symptoms of ADHD, lifetime symptoms of mood disorders, other comorbid conditions, and sociodemographic data.

RESULTS: According to the Mood Disorder Questionnaire (MDQ), 50.6% of the ADHD patients screened positive for BSD, compared to 8.3% of the controls. In comparison, the prevalence of BSD according to DSM-IV in a subsample of interviewed patients (n = 50) was 32%. In the whole study sample (N = 927), an ADHD diagnosis was the strongest predictor for screening positive on the MDQ (OR = 5.0, P < .001), but the correlation between dimensional symptom levels of ADHD and of BSD was strongest in the control group (Pearson correlation r = 0.7, P < .001 vs r = 0.3, P < .001). Patients screening positive on the MDQ had significantly more drug problems, higher ADHD symptom scores, and lower educational and occupational levels.

CONCLUSIONS: Our findings illustrate the close relationship between some symptoms of BSD and ADHD in adults. In clinical and research settings, patients screening positive for BSD should be assessed for a possible underlying or coexisting ADHD condition and vice versa.