Seasonal mood variation in youth and young adults with bipolar spectrum disorder: A longitudinal prospective analysis.

Objective: To determine whether there are latitude and seasonal differences in the prevalence of mood episodes (depression and mania) in youth and young adults with Bipolar Spectrum Disorder (BD).

Methods: Mood polarity was prospectively evaluated in 413 participants with BD. Participants were enrolled in the Course and Outcome of Bipolar Youth (COBY) study at three sites (University of California Los Angeles-UCLA, Brown University, and the University of Pittsburgh Medical Center-UPMC) and interviewed on average every 7 months for an average of 91.9 months (range: 6-228 months), with a total of 274,123 weekly mood ratings. Associations between light exposure and mood polarity were estimated using generalized linear mixed models with time-varying covariates, considering the latitude and seasonality of the study sites and other potential confounders.

Results: Average age at intake and at last assessment was 12.6 ± 3.3 and 27.2 ± 4.8 years-old, respectively. There were significantly more depressive episodes during winter than during summer, spring, and autumn. Considering latitude, UCLA showed significantly lower prevalence of depressive episodes, and an absence of seasonal pattern of depression, compared to the Brown/UPMC sites. For the entire sample, there were more manic/hypomanic episodes during summer than during winter. However, there were no significant between site seasonal differences in the prevalence of manic/hypomanic episodes.

Conclusions: Depressive episodes are more prevalent during the winter and although less significant, manic/hypomanic episodes during the summer. Awareness and interventions to prevent or ameliorate the effects of seasonal variations in mood changes in BD are warranted.