It is well established that major depressive disorder (MDD) is partly heritable. We present a genome-wide linkage study aiming to find regions on the genome that influence the vulnerability for MDD. Our sample consists of 110 Australian and 23 Dutch pedigrees with two or more siblings affected with MDD (total N = 278). Linkage analysis was carried out in MERLIN. Three regions showed suggestive linkage signals. The highest LOD-score of 2.1 was found on chromosome 17 at 52.6 cM along with LOD scores of 1.9 and 1.7 on chromosome 8 at 2.7 cM and chromosome 2 at 90.6 cM, respectively. The result on chromosome 8 seems most promising as two previous studies also found linkage in this region, once suggestive and once significant. The linkage peak on chromosome 17 harbors the serotonin transporter gene. In the Australian and Dutch sample, the serotonin transporter length polymorphism did not show evidence for association, thus other genes in this region or other polymorphisms in the serotonin transporter gene might be associated with MDD. Further replication is needed to establish the relevance of our linkage finding on chromosome 2
