MedWire News: US study findings suggest that attention deficit hyperactivity disorder (ADHD) is a risk factor for switching from unipolar to bipolar disorder (BD).
The study also shows that switches can be predicted by the presence of baseline conduct disorder, school behavior problems, and a family history of mood disorders.
“The finding that ADHD is a risk factor for switches from unipolar to bipolar disorder is consistent with a body of literature from pediatric and adult studies of individuals with BD and those with ADHD documenting a high and bidirectional overlap between BD and ADHD,” say Joseph Biederman (Harvard Medical School, Boston, Massachusetts) and co-authors.
For the study, the researchers used data from two large controlled longitudinal family studies of boys and girls with and without ADHD and their siblings. In total, 168 individuals with a lifetime history of unipolar major depressive disorder (MDD) - 53 controls, 115 ADHD - were followed up over a 7-year period and comparisons were made between those who did and did not switch to BP-I [expand].
A significantly higher number of ADHD patients with unipolar MDD (n=105) switched to BD at follow-up compared with controls, at 27.6% versus 6.0%. Those with subthreshold BP-I disorder at baseline had a significantly increased risk for progressing to full BP-I disorder at follow-up compared with those who did not (70% vs 17%).
Individuals who switched to BD at follow-up were significantly more likely to have comorbid conduct disorder (34% vs 14%) and school behavior problems (83% vs 59%) at baseline compared with those who did not switch.
In addition, a significantly higher rate of parental mood disorders was present in individuals who switched from unipolar MDD to BD than those who did not, at 68% versus 35%.
Biederman and team further found an additive risk for the significant predictors of bipolar switches, such that only 5% of individuals with no risk factors switched to BD, which increased to 24% and 32% with two and three factors, respectively.
“Clinicians should monitor closely patients with ADHD and comorbid MDD with multiple risk factors for bipolar switches,” conclude the authors in the Journal of Affective Disorders.
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