PARIS (AFP) - Male babies born shorter than average were more than twice as likely to attempt suicide as adults, especially by violent means, according to a study released Thursday.

Even among men of normal height who began life as newborns less than 47 centimetres (18.5 inches) long, the link with suicide remained almost as strong, said the study, published in the British Journal of Epidemiology and Community Health.

Weight at birth was also factor in the likelihood that a man would at some point try to take his own life, even more so when combined with below-average length.

Men who weighed under 2500 grammes (5.5 pounds) but who reached normal height were more than 2.5 times as likely to make a violent suicide attempt.

And premature babies -- both small and underweight -- were, as adults, more than four times as likely to attempt violent suicide than persons born after 38 to 40 weeks of pregnancy.

Violent suicides attempts were defined as those involving hanging, the use of a firearm or knives, jumping from a height or in front of vehicles, and drowning.

The study, led by Ellenor Mittendorfer Rutz of the Karolinska Institute in Stockholm, also found that height was a factor in suicide attempts independent of birth weight or size.

Short men, even if normal height when babies, were more than half again as likely to try to do themselves in. More generally, the taller a man was, the less likely he was to attempt suicide.

The study is based on national registration data in Sweden covering nearly 320,000 males born between 1973 and 1980.

The researchers speculated that the brain chemical serotonin may account for their findings.

Serotonin is critical for brain development, and low levels have been linked to aggressive, impulsive and suicidal behaviour. Several anti-depressant drugs regulate serotonin levels.

"Children born preterm show damage in various parts of the brain," including one -- the prefrontal cortex -- that is thought to be the site of changes in the serotonin metabolism of those who commit suicide, the authors conclude.

The study also said serotonin levels may be affected by other factors restricting growth in the womb, such as maternal drug and alcohol abuse, or malnutrition.