Columbia University professor of translational neuroscience Prof John Mann told the Royal Australian and New Zealand College of Psychiatrists conference in Queenstown yesterday suicide took an estimated million lives a year in the Western world, with two-thirds of attempts succeeding.
Attempts could be prevented through recognition, diagnosis and identifying high risk patients, he said.
"Aggressive traits and major depression are linked to suicide attempts. When the two come together, it makes for a dangerous combination."
Childhood suffering was directly associated with an increased risk of depression and suicide attempts.
"Childhood adversity affects adult stress levels. You are more likely to become pessimistic and therefore more likely to make a suicide attempt."
An adult's stress response system was moulded by genetic make-up as well as childhood experiences.
Although early-life experiences could have enduring formative effects on the brain, not everybody was vulnerable to childhood adversity.
"Part of that is genetic and part of that is others' response to adversity around you," Prof Mann said.
Males were twice as likely to attempt suicide and were more likely to succeed, because they planned more carefully.
"Men are very good at not telling you what is on their mind if they are going to attempt to kill themselves."
Other factors which contributed to a suicide attempt were genetics, alcohol and drug abuse, the quality of health care and depression.
Alcohol played a crucial role, if not triggering an attempt, he said.
"In countries where alcohol intake is higher, so is the suicide rate."
Prof Mann also said low serotonin levels in the brain could increase the risk of suicide by four and-half times, and also increase the success rate of an attempt. From serotonin levels, a psychiatrist could make predictions on the likelihood of a suicide attempt.
Religion had the reverse effect on suicidal intentions, he said.
"Religion and belief suicide is not the right thing to do holds a lot of people back from killing themselves."
