From the Editor

Seasonality of birth and psychiatric illness

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And now for the risk of psychi­atric disorders and month or season of birth. Here, too, there are multiple published reports:

  • Higher social anhedonia and schizoid features among persons born in June and July16
  • Higher autism rates for children conceived in December to March compared with those conceived during summer months17
  • In contrast to the above report, the risk of autism spectrum disorders in the United Kingdom was higher for those born in summer18
  • Another study labeled seasonality of birth in autism as “fiction”!19
  • Significant spring births for persons with anxiety20
  • Highest occurrence of postpartum depression in December21
  • High prepartum depression in winter and postpartum depression in fall22
  • Lower performance IQ among spring births23
  • Disproportionate excess of births in April, May, and June for those who die by suicide24
  • Suicide by burning oneself is higher among individuals born in January compared with any other month25
  • Relative increase in March and August births among patients with anorexia26
  • Season of birth is a predictor of emotional and behavioral regulation27
  • Serotonin metabolites show a peak in spring and a trough in fall28
  • Increase of spring births in individuals with Down syndrome29
  • Excess of spring births among patients with Alzheimer’s disease.30

As with the seasonality of medical illness risk, the association of the month or season of birth with psychiatric disorders may be based on skewed samples or simply a chance finding. However, there may be some seasonal environmental factors that could increase the risk for disorders of the body or the brain/mind. The most plausible factors may be season-related fetal developmental disruptions caused by maternal infection, diet, lack of sunlight, temperature, substance use, or immune dysregulation from comorbid medical conditions during pregnancy. Some researchers have speculated that fluctuations in the availability of various fresh fruits and vegetables during certain seasons of the year may influence fetal development or increase the susceptibility to some medical disorders. This may be at the time of conception or during the 2nd trimester of pregnancy, when the brain develops.

On the other hand, those studies, published in peer-reviewed journals, may constitute a sophisticated form of “psychiatric astrology” whose credibility could be as suspect as the imaginative predictions of one’s horoscope in the daily newspaper…

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