Segregation and linkage analysis of a large kindred of unipolar depression.

We studied segregation and linkage in a large kindred of unipolar depression. We subtyped the kindred on the basis of best fit to a single gene model and found that the cluster of "definite and probable depression, alcoholism, and drug dependency" gave the best fit. Since this is essentially the definition of depression spectrum disease (DSD), this was considered to be a DSD kindred. Using this definition of "affected" the genetic model provided a better fit to the data than the environmental model, although the difference was not statistically significant. A linkage analysis using 30 genetic markers did not suggest linkage at any of the loci tested. Finally, there was no evidence for an association between DSD and any of the 30 genetic markers.