Effects of Family History and Place and Season of Birth on the Risk of Schizophrenia

Author: Mortensen, Dr. Preben Bo; Pedersen, Carsten Bocker, et al.
Abstract: Although a family history of schizophrenia is the best-established risk factor for schizophrenia. environmental factors such as the place and season of birth may also be important. Using data from the Civil Registration System in Denmark, we established a population-based cohort of 1.75 million persons whose mothers were Danish women born between 1935 and 1978. We linked this cohort to the Danish Psychiatric Central Register and identified 2669 cases of schizophrenia among cohort members and additional cases among their parents. Results: the respective relative risks of schizophrenia for persons with a mother, father, or sibling who had schizophrenia were 9.31 {95 percent confidence interval, 7.24 to 11.96), 7.20 {95 percent confidence interval, 5.10 to 10.16), and 6.99 {95 percent confidence interval, 5.38 to 9.09), as compared with persons with no affected parents or siblings. The risk of schizophrenia was associated with the degree of urbanisation of the place of birth {relative risk for the capital vs. rural areas, 2.40; 95 percent confidence interval, 2.13 to 2.70). The risk was also significantly associated with the season of birth; it was highest for births in February and March and lowest for births in August and September. The population- attributable risk was 5.5 percent for a history of schizophrenia in a parent or sibling, 34.6 percent for urban place of birth, and 10.5 percent for the season of birth. Conclusions: Although a history of schizophrenia in a parent or sibling is associated with the highest relative risk of having the disease, the place and season of birth account for many more cases on a population basis. {N Engl J Med 1999;340:603-8.) {Copyright 1999, Massachusetts Medical Society.)
Keywords: season of birth, schizophrenia
Notes:This article was first published in The New England Journal of Medicine, Vol 340: 603-608 (Feb 25, 1999)
It is accompanied in Correlation Vol.18,1 by an Afterword by Dr. Frank McGillion pp 59 – 61
Publication: Correlation: Astrological Association Journal of Research In Astrology
Issue: Volume 18, Issue 1
Dated: 1999
Pages: pages 47 – 58