ELSEVIER Psychiatry Research 64 (1996) 11-17 PSYCHIATRY RESEARCH Relationship of birth season to clinical features, family history, and obstetric complications in schizophrenia Daniel Dassaa, Pak C. Sham*b, Jim van Osb, Kathryn Abelb, Peter Jonesb, Robin M. Murrayb zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQ ‘Dt?papartement de Psychiatric, C.H. I/. Timone, Boulevard Jean Moulin, 13385 Marseille Ct!deu 5, France ‘Department of Psychological Medicine, Institute of Psychiatry, De Crespigny Park, Denmark Hill, London SE5 8AF, UK Received 27 June 1995; revised 22 February 1996; accepted 11 May 1996 Abstract Birth in late winter and spring has been consistently shown to be a risk factor of schizophrenia. The relationship of late winter/spring birth to clinical characteristics and other putative risk factors, such as family history and obstetric complications, may provide clues to etiology. Data relating to season of birth, clinical features, family history, and obstetric complications were analyzed for 19’2 patients with schizophrenia as defined by Research Diagnostic Criteria (including schizoaffective disorder). There was no significant association of season of birth with any of the psychopathological dimensions nor was there a significant association with obstetric variables or family history. However, winter-born schizophrenic patients who had a negative family history were more likely to have a history of obstetric complications. These findings suggest that obstetric complications associated with schizophrenia are perhaps the result of some seasonal risk factors important in those without a family history of the disorder. Keywords: Sex; Birth complications; Schizoaffective disorder; Genetics 1. Introduction It is well documented that the risk of schizophrenia is increased by 7-15% among indi- viduals born in the late winter and early spring (reviewed by Bradbury and Miller, 1985; Boyd et al., 1986; Hare, 1988). One possible explanation is that some seasonal factor impairs fetal brain de- velopment and increases the predisposition to *Corresponding author. Tel: +44 171 9193536; fax: +44 171 7019044. later schizophrenia. The most obvious candidate is exposure to viral infection in utero, because (1) respiratory viral infections are particularly com- mon in winter and (2) there have been seven reports of an association between maternal expo- sure to influenza during the second trimester of pregnancy and adult schizophrenia (Mednick et al., 1988; Barr et al., 1990; O’Callaghan et al., 1991b; Sham et al., 1992; Adams et al., 1993; Takei et al., 1994; Kunugi et al., 1995), although such an association was not detected in three other studies (Crow et al., 1992; Torrey et al., 1992; Selten and Slaets, 1994). 0169-2607/96/$15.00 0 1996 Elsevier Science Ireland Ltd. All rights reserved PII SO169-2607(96) 02868-S