STRESS may be one of the main causes of female infertility, preventing thousands of otherwise healthy women in Britain from starting a family.

Many women who struggle to conceive could increase their chances greatly by learning to cope more effectively with the stress of daily life, scientists said yesterday.

Research in the United States has shown that psychological treatment designed to relieve stress can achieve spectacular results, restoring fertility to women who do not ovulate or menstruate.

The findings suggest that teaching stress-reduction techniques could be one of the most effective ways of treating this condition, known as amenorrhea, which affects up to one in ten women of reproductive age, and is caused by stress about half of the time. The work could also be significant for a much larger group of women, who still ovulate and have periods, but whose fertility is impaired by the effects of stress, researchers told the European Society of Human Reproduction and Embryology conference in Prague.

“We think there are women who have sub-clinical forms of stress and who are infertile as a result, though they are hard to recognise,” said Professor Sarah Berga, of Emory University in Atlanta, who led the study. “Some have normal menstrual cycles, but still have insufficient progesterone to support a pregnancy.”

Other papers presented at the conference yesterday also found that reducing stress during IVF treatment can improve the chances of success.

One of the studies, from an Israeli team, found that entertaining patients with a clown after embryos were transferred to the womb, using humour to alleviate stress, increased pregnancy rates from 19.3 per cent to 35.5 per cent.

In Professor Berga’s study, 16 women aged between 20 and 35 with stress-related amenorrhea, none of whom had had a period for at least six months, were split into two groups. One group was observed but not treated, while the other eight women were given a 20-week course of cognitive behavioural therapy, a “talking treatment” in which strategies for coping with stress are taught.

“A staggering 80 per cent of the women who received CBT started to ovulate again, as opposed to only 25 per cent of those randomised to observation,” Professor Berga said.

“This study underlines the important contribution that lifestyle factors make in determining overall health and reproductive health in particular.”

Two of the women who had the cognitive behaviour therapy responded so well that they became pregnant soon afterwards, where previously they had not been able to ovulate.

The treatment appeared to reduce levels of cortisol, a key stress hormone that was higher than normal in all the patients at the outset of the study. There was no corresponding decline in the untreated group.

Though the results come from a very small trial, and need to be confirmed by larger studies, they offer the best evidence yet that behavioural therapy to combat stress can restore fertility without recourse to hormonal drugs or IVF.

Professor Berga’s work also fits with the outcome of her previous research on monkeys. This found that stress, which was induced by changing the animals’ living arrangements on a regular basis, often induced amenorrhea, particularly when combined with poor diet and excessive exercise. Both behaviours are common among women with high stress levels.

She is about to start a much larger investigation of up to 4,000 American nurses, in which levels of the stress hormone cortisol will be checked against reproductive hormones that work as indicators of a healthy menstrual cycle. “If the study confirms our earlier results, we will have very strong evidence for offering stress reduction as an effective therapy for a significant group of infertile women,” she said.

The women in the study were generally young professionals with no obvious signs that they were stressed. All were of normal body weight and did not suffer from eating disorders, which are known to cause amenorrhea.

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