Seasonality of birth in patients with mood disorders in Japan

Background: Findings about seasonality of birth in individuals with mood di sorders have been inconsistent. Methods: Data were collected from the gover nmental statistics, the Patient Survey in Japan in 1996. The number of pati ents with mood disorders was 13,969. We obtained information about each pat ient's date of birth, sex, and diagnosis according to ICD-10. Distributions of monthly bir th numbers of patients with mood disorders were compared to those of the general population. Results: Birth excess was observed from w inter to early-spring in both sexes, compared to births of the general popu lation. The magnitude of the excess was larger in females than in males. Al though the same tendencies were observed in patients with bipolar disorder and depressive disorder, the differences were more marked in females. Limit ations: Insufficient birth data in the general population before 1940 and h ospital diagnosis. Conclusion: Among Japanese patients with mood disorders, there are excess births from winter to early-spring, compared to the gener al population. This difference is more marked in females than in males. (C) 2000 Elsevier Science B.V. All rights reserved.