Susceptibility loci for bipolar affective disorder on chromosome 18? A review and a study of Danish families

Chromosome 18 is one of the most promising chromosomes in the search for susceptibility genes for bipolar disorder based on results from cytogenetic, linkage, and association studies. Susceptibility loci on chromosome 18p and 18q have been suggested for bipolar affective disorder. We present a review of published studies which suggests that it is presently unclear whether one or more susceptibility loci on chromosome 18 exist, and that their more accurate localization is unknown. The present study investigated 27 DNA markers on chromosome 18 in two Danish families with bipolar affective disorder. We found positive lod scores in the larger family for markers on chromosome 18q12, especially for the affection status model which only includes bipolar patients. The highest lod score found was for marker D18S67, 1.83 at 0.05 recombination fraction.