A particular gene variant might make women more vulnerable to alcoholism, researchers at the Universities of Bonn and Sweden's Karolinska Institute have.
According to their study, a gene in the endorphin metabolism is altered in a typical fashion more often in women alcoholics than in healthy women.
In mice also, endorphins seem to play an important role in the amount of alcohol consumed, particularly among females.
Endorphins are known as 'happiness' hormones and they activate what is known as the reward system in the brain and thereby ensure a good mood.
Without these hormones, a person should be going easy on the alcohol, according to researchers' theory.
Researchers tested this hypothesis by examining mice that could not produce any endorphins due to a genetic mutation.
The laboratory mice had the choice of quenching their thirst with pure water or an ethanol solution.
"Overall, mice without endorphins drank less alcohol than their relatives with endorphins,' Dr. Ildiko Racz from the Bonn Institute of Molecular Psychiatry explains.
The endorphin effect was particularly marked in female mice. Normally these tend to hit the bottle more than males.
"But without endorphins, the decrease in their desire for alcohol was particularly drastic." Dr Racz adds.
On contrary, in males the absence of the endorphins made less difference.
Researchers then scrutinised genes, which are important in the human endorphin metabolism.
For this, they analysed blood samples of just short of a total of 500 female and male alcoholics for peculiarities.
"We were able to show that two genetic changes in the genes of female alcoholics occurred significantly more frequently than in healthy women. We don't know what the exact effect of these changes is," Dr Racz said.
By contrast, the scientists did not find any changes that indicated a contribution of endorphins in male alcoholics.
Women with a particular genetic make-up could therefore be at greater risk of becoming dependent on alcohol.
"Today we estimate the influence of the genes in this disease to be at least 50 per cent," Dr. Racz said.
However, she warns against exaggerating the results.
"We can only evaluate how large the influence of the genetic mutations we found really is after carrying out further research," Dr. Racz said.
At least it seems to be a bit clearer now that endorphins really do play a role in the development of ethanol addiction.
The study is published in the current issue of the journal Biological Psychiatry.