Seasonality of schizophrenia births in the Japanese population: Increased winter births possibly confined to the north area

Mamoru Tochigi, Takashi Onai, Kaori Narita, Hiroyuki Hibino, Mark Rogers, Tadashi Umekage, Kazuhisa Kohda, Toshiyuki Otani, Ryo Kanamori, Nobumasa Kato, Tsukasa Sasaki

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


A number of North American and European studies have observed a higher proportion of winter births in schizophrenia patients. Thus, seasonal fluctuation of unknown environmental factors may affect brain development in ways that alter susceptibility to schizophrenia. Specification of these factors may help elucidate the etiopathological mechanism of the disease, about which little is certain. A small number of studies have investigated this issue in Asian populations, and the findings are not as consistent as those of Western populations. No remarkable excess of winter births has been observed in Japanese or Korean studies, while some studies have reported a significant decrease of summer births. We further investigated the issue in Japanese patients with schizophrenia (n=3927). No significant excess of winter births was observed, but a decrease in the summer births was found in male subjects. This is largely consistent with previous Japanese studies; however, when the subjects were confined to those born in a colder and higher latitude area of Japan (n=1338), a consistent trend for both a winter increase, and a summer decrease, was found. However, the results did not consistently reach statistical significance, possibly due to the lack of statistical power. Environmental factors that correlate with latitude might play a role in the development of the seasonality of births in schizophrenia. Further studies in a larger sample size are required to test these possibilities.

Original languageEnglish
Pages (from-to)433-438
Number of pages6
JournalSchizophrenia Research
Issue number2-3
Publication statusPublished - 2005 Jun 15
Externally publishedYes


  • Japanese population
  • Latitude
  • Meteorological factors
  • Schizophrenia
  • Season of birth

ASJC Scopus subject areas

  • Psychiatry and Mental health
  • Biological Psychiatry


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