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March 1993

Reply to 'A Genetic Study of Male Sexual Orientation'

Arch Gen Psychiatry. 1993;50(3):240. doi:10.1001/archpsyc.1993.01820150090010

To the Editor.—  I am surprised that the article by Bailey and Pillard1 was carried out, written, and published in the December 1991 edition of the ARCHIVES with so little regard for the problems in the numerous studies of the genetics of schizophrenia based on the comparison of incidence in monozygotic (MZ) and dizygotic (DZ) twins as well as the various adoption studies that have caused so much misunderstanding and confusion in the field. Are we now to go through the same misapplications of methodology and statistics to homosexuality?Kallmann2 misled psychiatrists into the belief that schizophrenic disorders were almost entirely genetically determined. His very high concordance rate for MZ twins appears to have been due to his sampling of twins hospitalized for schizophrenia where concordance was generally only noted when both twins were schizophrenic. Further, the fact that DZ twin sisters were almost as concordant as MZ