It's the time of the month for a drink

Many women who like a drink notice that their ability to handle alcohol varies through the month, but the evidence for this has always been largely anecdotal.

Now researchers from the Netherlands have brought together a body of evidence that suggests these social observations are based in biological fact.

Women may indeed be less able to handle the effects of alcohol in the four days leading up to menstruation than at other times. They may also need more alcohol than usual to experience its pleasurable effects in the middle of their menstrual cycle.

In a review of research on women and alcohol, the Netherlands Research Group on Addictive Behaviours found that levels of alcohol in the blood appear highest in the pre-menstrual phase, usually defined as the four days before the onset of menstruation, and that blood alcohol levels are particularly high immediately before the onset of the menstrual flow.

At this time, it appears, a woman's body is least able to eliminate alcohol. It gradually recovers this ability, reaching a peak between 12 and five days before the onset of the next period.

The research also suggests that women drink most heavily in this 12-to- five-day gap. It may be that women need to drink more at this time to obtain the same effect.

The idea that women's hormones may influence the way their bodies dispose of alcohol should come as no surprise; in pregnancy the body's ability to eliminate drugs, including alcohol, is reduced.

The hormonal cycle is known to change the way other drugs affect women's bodies. The blood alcohol levels of women on many psychiatric drugs are much higher than those of men taking the same dose - with weight differences taken into account.

Women also appear to eliminate from their bodies sedative drugs such as Valium more slowly than men. A standard dose of Valium can produce in some women a relatively intoxicated state during the time of menstrual flow.

All this points to the impact of alcohol being more unpredictable for women than it is for men - as well as having all sorts of fascinating implications for women. Could it, for example, influence legal defences in drink-driving cases?

Probably not, but who knows? What we do know is that alcohol in large quantities almost certainly affects the menstrual cycle; alcoholic women are frequently also infertile.

The writer is a consultant psychiatrist.