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September 1990

Influenza and Schizophrenia: Helsinki vs Edinburgh

Author Affiliations

Psykologisk Institute Kommunehospitalet 1399 Copenhagen, Denmark
Department of Psychology Loyola Marymount University 7101 W 80th St Los Angeles, CA 90045
Department of Psychiatry University of Helsinki Lapinlahdentie, SF 00180 Helsinki, Finland
Social Science Research Institute University of Southern California DRB 101, MC 1111 Los Angeles, CA 90089-1111

Arch Gen Psychiatry. 1990;47(9):875-876. doi:10.1001/archpsyc.1990.01810210083013

To the Editor.—  Kendell and Kemp1 conclude that the three studies they report do not support the influenza A virus hypothesis in schizophrenia. We cannot accept their conclusions due to serious inadequacies in their data sources and methods.Kendell and Kemp reason that the severe June and November 1918 and March 1919 influenza epidemics that devastated Scotland should have increased the rate of schizophrenia among those exposed during gestation. To identify people with schizophrenia born in 1918 and 1919, they used a national Scottish register of psychiatric hospitalizations. They inspected their data visually and concluded that there was no increase in the number of people born with schizophrenia in 1918 and 1919. For the period in question, however, the register did not record date of birth; only the patient's report of his or her age was recorded. Year of birth was calculated by subtracting the age reported from the

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