Parental sex effects in bipolar affective disorder pedigrees.

A combined linkage analysis was performed on chromosome 18 data and produced modest evidence in three of four data sets for linkage of a susceptibility locus for bipolar disorder to markers on chromosome 18p. All data sets showed a preponderance of females among affected individuals. When this was taken into account, no convincing evidence was obtained for excess transmission from mothers compared to fathers. In addition, there was no evidence for differences in the proportions of affected offspring from affected fathers and mothers. We conclude that these combined data do not support previous suggestions of a maternal effect on transmission of bipolar affective disorder.