Bipolar disorder with seasonal pattern: clinical characteristics and gender influences

Bipolar disorder (BD) has a multifactorial etiology with heterogeneous clinical presentations. Around 25% of BD patients may present with a depressive seasonal pattern (SP). However, there are limited scientific data on the prevalence of SP, its clinical manifestations, and any gender influence. Four hundred and fifty-two BD I and II cases (62% female), recruited from three French university-affiliated psychiatric departments, were assessed for SP. Clinical, treatment, and sociodemographic variables were obtained from structured interviews. One hundred and two (23%) cases met DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) criteria for SP, with similar frequency according to gender. Multivariate analysis showed a significant association between SP and BD II (odds ratio [OR] = 1.99, p = 0.01), lifetime history of rapid cycling (OR = 2.05, p = 0.02), eating disorders (OR = 2.94, p = 0.003), and total number of depressive episodes (OR = 1.13, p = 0.002). Seventy-one percent of cases were correctly classified by this analysis. However, when stratifying the analyses by gender, SP was associated with BD II subtype (OR = 2.89, p = 0.017) and total number of depressive episodes (OR = 1.21, p = 0.0018) in males but with rapid cycling (OR = 3.02, p = 0.0027) and eating disorders (OR = 2.60, p = 0.016) in females. This is the first study to identify different associations between SP and clinical characteristics of BD according to gender. The authors suggest that SP represents a potentially important specifier of BD. These findings indicate that seasonality may reflect increased severity or complexity of disorder.