Genome-wide linkage analysis was carried out in a sample of 497 sib pairs concordant for recurrent major depressive disorder (MDD). There was suggestive evidence for linkage on chromosome 1p36 where the LOD score for female-female pairs exceeded 3 (but reduced to 2.73 when corrected for multiple testing). The region includes a gene, MTHFR, that in previous studies has been associated with depressive symptoms. Two other regions, on chromosomes 12q23.3-q24.11 and 13q31.1-q31.3, showed evidence for linkage with a nominal P<0.01. The 12q peak overlaps with a region previously implicated by linkage studies of unipolar and bipolar disorders and contains a gene, DAO, that has been associated with both bipolar disorder and schizophrenia. The 13q peak lies within a region previously linked strongly to panic disorder. A fourth modest peak with an LOD of greater than 1 on chromosome 15q lies within a region that showed genome-wide significant evidence of a recurrent depression locus in a previous sib-pair study. Both the 12q and the 15q findings remained significant at genome-wide level when the data from the present study and the previous reports were combine
