White Matter Lesions and Season of Birth of Patients With Bipolar Affective Disorder

OBJECTIVE: It is established that patients with bipolar disorder have an excess of births in winter or early spring. The authors investigated a link between season of birth and white matter lesions with magnetic resonance imaging (MRI). METHOD: T₂-weighted and proton density MRI scans were examined for 79 patients with bipolar disorder (DSM-IV) for the presence of deep subcortical and periventricular white matter lesions. The birth seasons of patients with white matter lesions were compared with those of the general population. RESULTS: Thirteen subjects exhibited deep subcortical white matter lesions, of whom nine (69.2%) were born in the winter months (January to March). Seven of these patients remained symptomatic, despite adequate treatment for more than 2 years. CONCLUSIONS: Birth season, illness outcome, and deep subcortical white matter lesions appear to be closely linked. Deep subcortical white matter lesions may be a marker of a toxic or infective insult in utero.