Linkage Analyses ofChromosome18MarkersDo NotIdentify a MajorSusceptibility LocusforBipolar Affective Disorder inthe OldOrderAmish

Summary Previously reported linkage ofbipolar affective disorder toDNAmarkers inthepericentromeric region ofchromosome18wasreexamined inalarger homogeneous sample ofOldOrderAmishfamilies. Fourmarkers (D18S21, D18S53, D18S44, andD18S40) wereexaminedinthree kindreds containing 31bipolar I(BPI) individuals. Although linkage findings werereplicated intheonepreviously studied Amish pedigree containing four BPIindividuals, linkage tothis region wasexcluded inthelarger sample. Ifasusceptibility locus forbipolar disorder islocated inthis region ofchromosome 18,it isofminor significance inthis population.