Schizophrenia's places and seasons

Science News, March 13, 1999 by B.B.

Environmental factors may outweigh genes as contributors to population rates of schizophrenia, a Danish study finds.

Epidemiologists led by Preben Bo Mortensen of Aarhus University Hospital in Risskov, Denmark, used government data sources to identify 2,669 cases of schizophrenia among all 1.75 million people whose mothers were Danish women born between 1935 and 1978. Schizophrenia's fragmentation of thought and emotion usually emerges in young adulthood.

The likelihood of developing schizophrenia was sharply higher among people with a mother, father, or sibling who had schizophrenia, compared with people who had no schizophrenia in their families, the researchers report in the Feb. 25 NEW ENGLAND JOURNAL OF MEDICINE. Mortensen and his coworkers also found that urban birth exerted a powerful impact on the schizophrenia rate. After that came birth in February and March, followed by a family history of schizophrenia.

These findings may reflect the influence of prenatal brain disruptions in response to factors such as exposure to infections and poor maternal nutrition, in causing schizophrenia (SN: 2/3/96, p. 68), says psychiatrist Nancy C. Andreasen of the University of Iowa in Iowa City.