A Technique for Comparing the Relative Importance of Season of Conception and Season of Birth: Application to Emotionally Disturbed Children

Abstract

Numerous studies have related psychiatric disturbance to season of birth. Barry and Barry (1961) cited nine independent studies which concluded that mentally ill persons, especially schizophrenics, tend to have been born during the first four months of the calendar year. Hare and Price (1969) reported more recent evidence of similar seasonal birth trends for large groups of hospitalized British schizophrenics and manic-depressives, as compared with neurotics. Barry and Barry (1964) later suggested that the seasonal birth pattern may be more relevant to middle and lower class schizophrenics than to upper class schizophrenics from private mental hospitals. Orme (1963) upheld this seasonality of birth pattern among less intelligent but not among more intelligent psychotics. Norris and Chowning (1962), who confirmed the seasonal birth pattern among Canadian schizophrenics from both public and private hospitals, observed that the significance of seasonal differences between schizophrenics and normal populations depends upon which population birth years are selected for comparison. Norris and Chowning therefore suggest that the seasonal birth trend among schizophrenics may be the result of random variations in birth rate together with post-hoc grouping of the particular years for comparison. While this interpretation and criticism is tenable for a given study, it has become less tenable as evidence converges from the many independent studies.