Intelligent young men are less likely to take their own lives than others, researchers suggest.
The government has set a target to cut suicide rates by 2010
Young men who scored low on intelligence tests were two to three times more likely to commit suicide, the Swedish-UK team found.
They followed nearly a million 18-year-old men, consigned to serve in the military, for up to 26 years.
The researchers told the British Medical Journal that problems in childhood might be an underlying cause.
Suicide accounts for a fifth of all deaths amongst young people aged 15-24 and is the second most common cause of death amongst young people after accidental death, according to the Samaritans.
Around 19,000 young people attempt suicide every year and about 700 of these die as a result.
While young women aged 15-19 are the group most likely to attempt suicide, young men are much more likely to die as a result of their suicide attempt, according to Mind.
Between 1971 and 1998, the suicide rate for women in England and Wales almost halved, while in the same period the rate for men almost doubled.
But latest figures show the suicide rate for young men has fallen to its lowest level for almost 20 years, having dropped almost 30% from its peak in 1998 to 8.6 deaths per 100,000 population.
Lead author Professor David Gunnell from the University of Bristol, working with colleagues at the Karolinska Institute in Sweden, said there was evidence suggesting intellectual performance is associated with psychiatric disorders such as schizophrenia and depression.
"But there have been few studies looking at intelligence and suicide," he said.
"This is the largest study to examine the issue.
"We found quite strong evidence of an association between performance on intelligence and subsequent suicide risk."
There were 2,811 suicides overall.
Better performance on tests of logic, language, spatial and technical skills was associated with a reduced risk of suicide.
The strongest link was with the logic test score, where the risk of suicide was three times higher in the lowest compared with the highest scorers.
Army recruits who performed poorly on the intelligence tests and had well educated parents also appeared to be a higher suicide risk.
The researchers believe influences on brain development during childhood might increase a person's risk of mental illness and hence suicide.
It might also be that children who experience crisis and are less able to adapt to it grow up to be at increased risk of suicide, they said.
"Intelligence may impact on their chances in life, such as the job they get, their financial security and their prospects of getting married.
"All of these factors could be important in suicide risk," said Professor Gunnell.
Sarah Nelson of the Samaritans welcomed the research, but with caution.
"It would be wrong to interpret this to mean if you are less intelligent then you are more likely to take your own life.
"People who do not perform as well on intelligence tests might be less able to problem solve and that might be a factor."
Sophie Corlett, Mind's Director of Policy, agreed saying: "People of different intellectual levels unfortunately commit suicide for a variety of reasons."
Marjorie Wallace of SANE said: "It is essential that any young person in this vulnerable group should be given urgent attention if and when they seek help.
"Currently, such young people can all too often be ignored until it is too late."
Professor Louis Appleby, the National Director of Mental Health, said the downward trend in male suicide was encouraging, but that continued work was needed to ensure it continued.