A third of men are believed to suffer from premature ejaculation
Men who suffer from premature ejaculation may be able to blame their genes, work suggests.
A study of nearly 200 Dutch men found those who climaxed too soon during intercourse had a version of a gene that controls the hormone serotonin.
Men with this version ejaculated twice as quickly as other men in the study.
Serotonin levels are what control the rapidity of ejaculation, say the Utrecht University researchers told the Journal of Sexual Medicine.
Not in the mind
The volunteers in Dr Marcel Waldinger's study were 89 men who had so-called primary premature ejaculation, meaning they had always suffered from it from their first sexual contact onwards.
For a month, their female partners were asked to use a stopwatch at home to measure the time until ejaculation each time they had intercourse.
The results were compared with 92 men with no history of such problems.
In the men with premature ejaculation, serotonin appeared to be less active between the nerves in the section of the brain that controls ejaculation.
Dr Waldinger says this low activity of the hormone means nerve signals do not transfer in the normal way in these men.
"This contradicts the idea, which has been common for years, that the primary form of premature ejaculation is a psychological disorder," he said.
The findings also mean it might be possible to treat the condition with gene therapy, he said.
Paula Hall, a sexual psychotherapist for Relate, said: "Premature ejaculation is definitely not purely psychological.
"But there can be a psychological element. The acid test is how much control they have on their own. If the problem only occurs with their partner then it is more likely to be psychological."
She said men with primary premature ejaculation tended to be fast reactors generally.
"These men have very quick reflexes. They may be excellent at playing tennis or computer games, for example."
She said there was good evidence that serotonin was linked ejaculation and that researchers were developing drugs for the condition that prolong this hormone's action.
Currently there is no medication for the condition on the market.
Treatments involve counselling and the use of anti-depressants - not for depression but for their unexpected yet wanted side effect of delaying ejaculation.
A third of men are believed to suffer from premature ejaculation.