Climate and prevalence of mood disorders: a cross-national correlation study.

To the Editor: Seasonal climate variations are notably known to affect mood in both individuals with and individuals without mental disorders.1,2 Intriguingly, the prevalence of mood disorders differs greatly from one country to another. For example, lifetime prevalence has been measured at 21% in France and the United States, compared with under 5% in Nigeria.3 Since seasonal variations could affect the mood, we conducted the following study to examine whether some climate characteristics could, at least in part, explain the worldwide distribution of lifetime prevalence of mood disorders.