Tung-Ping Su, MD, of Taipei Veterans General Hospital, Taiwan, and colleagues conducted a longitudinal, follow-up study based on more than 56,000 young people without depression and 1,200 people with depression and comorbid ADHD.
Those with major depression and ADHD were 1.5 times more likely to develop bipolar disorder compared to the group without depression, the researchers reported in the journal Bipolar Disorders.
The rate of conversion from major depression to bipolar disorder before adulthood (<18 years old) was significantly higher among adolescents with comorbid ADHD, at 6.9% compared with 6.3% for those without ADHD. The rate of conversion in adulthood was also greater for those with comorbid ADHD, at 6.3% versus 5.2%.
Also, bipolar disorder was more common in those with depression and ADHD than depression alone — 18.9% versus 11.2%.
Additional “studies would be required to investigate the underlying mechanisms between ADHD comorbidity and diagnostic conversion from major depression to bipolar disorder,” the researchers wrote.
Young people with major depression have an increased risk of conversion to bipolar disorder if they have comorbid attention deficit/hyperactivity disorder (ADHD), suggest findings from a longitudinal follow-up study. The patients with comorbid ADHD were, on average, 6 years younger at the time major depression was diagnosed than their major depression-only counterparts.