The Genetics of Suicidal Behaviour

In medicine in general, establishing that an illness (or behaviour) has a genetic component requires evidence from clinical, twin, adoption and laboratory molecular genetic studies. Such studies exist in the suicide literature and their data suggest that there is a genetic component to suicidal behaviour. For example, it is now well established that a family history of suicide indicates that an individual is at raised risk for both completed suicide and attempts at suicide.Twin studies have shown that monozygotic twins who share 100% of their genes have a significantly greater concordance for both completed suicide and attempted suicide than dizygotic twins who share ony 50% of their genes. Adoption studies also suggest a genetic component to suicide. Most recently, laboratory molecular genetic studies have shown that a variant in the gene coding for tryptophan hydroxylase, the rate-limiting enzyme in the synthesis of the neurotransmitter serotonin, is associated with suicidal behaviour. The evidence now seems incontrovertible that there is a genetic contribution to suicidal behaviour.