Suicidal behaviour shows evidence of familial clustering and the twin data on completed suicide suggest moderate heritability. The extent to which the genetics of suicidal behaviour overlaps with the genetics of affective disorders is unclear but there is overwhelming evidence that both bipolar and unipolar disorder are substantially influenced by genes. So far, candidate gene studies of suicidality have provoked much interest, but recently, attention has also turned to candidate gene approaches to suicidal ideation emerging during antidepressant treatment. The advent of genome-wide association studies (GWAS) has had a major impact on studies of affective disorder with some provocative new findings. The GWAS approach is also beginning to be applied in the search for genes that underlie suicidal ideation and behaviour.

Genome-wide association studies have uncovered hundreds of loci associated with psychiatric disorders. Cross-disorder studies are among the prime ramifications of such research. Here, we discuss the methodology of the most widespread methods and their clinical utility with regard to diagnosis, prediction, disease aetiology and treatment in psychiatry.