There could be hundreds of genes which make people more likely to kill themselves and the trait is believed to run in the family, a study has found.
Scientists have discovered four genetic changes which are more common among people who have killed themselves.
And they say there are more than 200 others which are worth doing more research into to find out whether they have links to suicide.
The researchers hope being able to identify people who are naturally more at risk of taking their own lives will help them target mental help to the right places.
Researchers from University of Utah made the discovery by looking at the DNA of 1,300 people who had killed themselves in the state.
They found changes to certain genes – named SP110, AGBL2, SUCLA2 and APH1B – were found more often in people who had killed themselves than in other people.
As well as those four genes, there are another 207 which 'warrant further analysis,' the researchers said.
Scientists have already suggested suicidal tendencies can run in the family, but it has proved harder to pinpoint the exact genetic changes triggering them.
Finding those genes and the people who have a higher genetic risk could help mental health services intervene more effectively.
'Clearly genetics is only one part of risk when it comes to suicide,' said the study's lead author, Dr Hilary Coon.
LGBTQ TEENAGERS ARE THREE TIMES MORE LIKELY TO KILL THEMSELVES
LGBT adolescents are more likely than other kids their age to try to kill themselves, research revealed in October.
Children and teens who identify as sexual minorities face unique risks of bullying, discrimination and mental health issues in the US and abroad.
Data pooled from 35 earlier studies show that sexual minority youth were more than three times as likely to attempt suicide as heterosexual peers, researchers reported in JAMA Pediatrics.
The analysis involved a total of nearly 2.4 million heterosexual youth and 113,468 sexual minority youth, aged 12 to 20, from 10 countries.
Transgender adolescents were 5.87 times more likely, gay and lesbian adolescents were 3.71 times more likely and bisexual youth were 3.69 times more likely than heterosexual peers to attempt suicide.
'I think that a difficulty in self-acceptance and social stigmatization might be keys for understanding such elevation in the risk of self-threatening behaviors,' said the study's lead author, Dr Ester di Giacomo from the University of Milano-Bicocca.
'But we are hoping these discoveries will lead us to highly susceptible individuals so we can develop better interventions to help them circumvent this risk.'
Of the genes involved, one of them – APH1B – is believed to be linked to Alzheimer's disease, suggesting a possible link between the brain disease and suicide risk.
The DNA samples used were taken from distant relatives in 43 different families over nine generations in Utah.
This, the researchers said, meant they could examine people with similar DNA but different surroundings – so two members might have very similar genetics but not both be affected by the same events in the family, for example.
As well as the four genes identified in the study, 18 of the genes out of the 207 picked out by the researchers have already been linked to a person's risk of suicide in past studies.
And 15 of them have been linked to inflammatory health conditions, meaning there could be a link between those and suicide risk.
Suicide is the 10th leading cause of death in the United States, claiming the lives of 44,000 people a year.
And in the UK, suicide is the leading cause of death for males aged between five and 49, and women aged five to 34 years old.
'Past studies of families and twins informed us that there is significant genetic risk associated with suicide,' said Dr Douglas Gray, a senior author on the paper.
'Genes are like blueprints. The first step is to find the genes that increase risk. Identifying specific genes may lead to new treatments for those who suffer.'
Dr Coon added: 'We think these results are just the tip of the iceberg. We will continue to search for additional gene changes that lead to risk.'
The research was published in the journal Molecular Psychiatry.
This comes after the head of NHS said last month social media companies should be forced to pay a 'mental health levy' to help address problems linked to sites like Facebook and Instagram.
Simon Stevens, chief executive of NHS England, argues a financial contribution from social media sites would help to 'stem the tide of mental ill health' in the UK.