A genetic defect that impacts upon the growth of nerve cells may be the reason suicidal tendencies can run in the family, research suggests.
Previous research has pointed towards suicide being a hereditary condition, and the latest finding support that belief.
A total of 394 patients who were suffering with depression, including 113 who had attempted suicide, were tested as part of an investigation into generic variants. Healthy individuals from the general population had their DNA used as comparative data.
The results were confirmed by a follow-up study of more than 1,600 German and African–American patients, 270 of whom had attempted suicide.
Five single-letter changes in the genetic code were found to be significantly more common among individuals with a history of suicide attempts.
The variants, known as single nucleotide polymorphisms (SNPs), affected two genes associated with nerve cell formation and growth.
Carriers of the three most important mutations were 4.5 times more likely to attempt suicide than those without them.
The research was led by Dr Martin Kohli, formally at the Max Planck Institute of Psychiatry in Munich, Germany, and now at the John P Hussman Institute for Human Genomics in Miami, USA.
Reporting their findings in the journal Archives of General Psychiatry, the authors wrote: "The genetic risk factors for suicide appear to be independent from the underlying psychiatric disorder."