A simple blood test to identify these variations could allow doctors to intervene before people take their own life, the researchers believe.
'We have found a gene that we think could be really important for consistently identifying a range of behaviours from suicidal thoughts to attempts to completions', said lead author Dr Zachary Kaminsky, assistant professor of psychiatry and behavioural sciences at Johns Hopkins University School of Medicine.
The study, which was published in the American Journal of Psychiatry, looked at post-mortem brain samples from 98 mentally-ill people and 70 healthy people. The researchers found that those who had committed suicide had increased levels of methylation on a gene called SKA2. Methylation is a type of epigenetic modification that does not alter the gene sequence itself but can stop a particular gene from being expressed. In line with this, the researchers also found that those who had died from suicide had significantly reduced levels of the gene SKA2. SKA2 has previously been shown to be important in regulating the stress hormone cortisol in the brain.
In another part of the study the researchers found higher levels of methylation on the SKA2 gene in blood samples of living people who had suicidal thoughts. The researchers then developed a blood test that predicted which of the participants were experiencing suicidal thoughts with 80 percent accuracy.
'Suicide is a major preventable public health problem, but we have been stymied in our prevention efforts because we have no consistent way to predict those who are at an increased risk of killing themselves. With a test like ours we may be able to stem suicide rates by identifying those people and intervening early enough to head off catastrophe', said Dr Kaminsky.
However, the usefulness of such a test has been questioned as those with suicidal thoughts may be unlikely to come forward to be tested. Furthermore, although the researchers found a correlation between reduced SKA2 function and suicidal thoughts, a direct causal link between SKA2 and risk of suicide was not identified.
The researchers noted that these results will need to be confirmed in larger studies before entering the clinic.