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June 1981

X-Chromosome Markers in Bipolar Illness

Author Affiliations

Department of Psychiatry Cliniques Universitaires de Bruxelles Erasme Hospital Free University of Brussels 808 Route de Lennick Brussels 1070, Belgium

Arch Gen Psychiatry. 1981;38(6):719. doi:10.1001/archpsyc.1981.01780310119013

To the Editor.—  I have been puzzled by Gershon's letter to the editor (Archives 1980;37:1200) that raises some issues about our work on X-chromosome markers in bipolar illness. There is indeed a discrepancy between the study of Gershon and colleagues1 and our linkage studies.2.3 The samples were not collected in the same population and during the same period of time for both studies. Furthermore, the sample sizes are not comparable either. In our early studies,2.3 we demonstrated close linkage between bipolar illness and color blindness in 17 informative kindreds and the absence of such linkage for unipolar illness in a controlled sample of 14 informative kindreds. The recent series by Gershon et al1 is limited to six pedigrees and to bipolar illness. As Gershon carefully points out in his letter, his series is too small to rule out X-linkage as a possible mode of transmission of bipolar