The birth seasonality effect in nonschizophrenic psychiatric patients.

Several studies have suggested that patients with affective, neurotic, and personality disorders are particularly likely to have been born during the early months of the year. They suggest that seasonal factors may play a role in the etiologies of these disorders. However, Lewis and Griffin (1981) have suggested that the reported seasonal exaggerations in psychiatric patients' birthrates simply may reflect artifacts. We searched for seasonal trends in the birth patterns of neurotics (N = 989), alcoholics (N = 2,870), affective disorders (N = 320) and personality disorders (N = 713), both before and after controlling for these artifacts. No significant effect appeared.