Suicidal behavior is a leading cause of death and disability in the United States. Suicide is influenced by a variety of factors, including psychological, social, moral, political, and economic influences. Heredity has also been linked to suicidal thoughts and actions. Now, new evidence suggests that suicide attempt is linked to a specific gene.

In 2007, the most recent year with available data, suicide was the 11th leading cause of death in the United States, claiming nearly 35,000 lives (Europe has it worse). The total cost of suicidal behavior (fatal and nonfatal outcomes) was approximately $33 billion in 2000. The suicide rate for males is roughly four times higher than it is for females. Beginning in adolescence, suicide rates rise steadily with increasing age and peak among the 40- to 54-year-old age group. Suicide rates decline in older populations.

No one cause is linked to suicide, but self-directed harm has been associated with environmental and genetic influences. In particular, substance abuse disorders, depressive disorders, and bipolar disorder are linked to inherited conditions and associated with an increased risk of suicide. The present study, published in Molecular Psychiatry, reports an association between attempted suicide and a gene on chromosome 2, substantiating the heritable component of suicidal behavior.

The study evaluated the entire genomes of patients with bipolar disorder who had attempted suicide (n=1201) and those who had not (n=1497). In total, there were more than 2500 regions located on various chromosomes that showed significant associations with suicidal behavior. The strongest association was with a region on chromosome 2 containing the ACP1 gene. This gene encodes for a signaling protein (tyrosine phosphatase) produced in the brain. Alterations in this gene promote the up-regulation of signaling proteins that influence cell survival and synaptic plasticity; it is also linked to immune system function and carcinogenesis. Tyrosine phosphatase also decreases the activation of a signaling pathway that is activated by lithium. (Lithium is used to treat bipolar disorder and has antisuicidal properties.) In people who have attempted or completed suicide, expression of this gene is high.

Most suicide prevention efforts focus on counseling, education, and clinical intervention of disorders known to increase suicidal behavior. Identifying specific genes that increase susceptibility to suicide could lead to the development of novel, gene-targeted therapies for suicide prevention. Larger samples sizes including different populations are needed to confirm these findings and direct therapies toward individuals predisposed to suicide.

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