By science correspondent Christine McGourty

Scientists in France and Switzerland say they have found genes that may cause suicidal behaviour.

Two studies of patients in psychiatric hospitals indicated those with alterations in one of two genes were more likely to attempt suicide.

It is clear that among sufferers of major depression, some people are far more prone to suicidal behaviour than others.

Scientists want to find out if the difference lies in their genes.

Unregulated anxiety levels

The two teams studied patients in psychiatric hospitals their respective countries and found that attempted suicide rates were higher among those with particular genetic variations.

The altered genes disrupted the brain's natural mechanism for producing the chemical serotonin, which is known to regulate mood and anxiety levels.

Scientists in London now hope to find out if genetic variations could at least partly explain the different suicide rates across Europe.

They are highest in Slovenia, Finland and Hungary and low in Croatia, Italy and Spain, with UK levels at about the European average.