Women do not put their mental health at risk by having an abortion, according to an authoritative study that will undermine the campaign to tighten the UK's abortion laws.

A comprehensive review of research by the American Psychological Association (APA), one of the world's most influential mental health bodies, found no evidence that the majority of abortions cause psychiatric problems.

By challenging a key scientific argument for reform, the findings will hinder the latest effort to make it harder for British women to obtain terminations, which is to be debated by the House of Commons in October.

Anti-abortion MPs have tabled an amendment to the Human Fertilisation and Embryology Bill that would require all women to be counselled about psychiatric risks before they can be cleared to have a termination. They cite research suggesting that mental health issues such as depression and anxiety are more common among women who have had abortions.

The APA report said that the findings of such studies were unreliable because they either failed to distinguish between abortions of wanted and unwanted pregnancies, or they did not consider factors such as poverty and drug use that raise the likelihood both of having an abortion and suffering mental illness.

The APA found “no credible evidence” that single abortions could directly cause mental health problems among adults with unwanted pregnancies. It called for more well-designed studies to investigate the issue.

Even the evidence for adverse psychiatric effects of multiple abortions was equivocal, it found. Higher rates of mental illness among such women could be explained by social factors, such as poverty or drug use that also put them at higher risk of unplanned and unwanted pregnancy.

Brenda Major, who chaired the task force, said: “The best scientific evidence published indicates that among adult women who have an unplanned pregnancy the relative risk of mental health problems is no greater if they have a single elective first-trimester abortion or deliver that pregnancy.

“The evidence regarding the relative mental health risks associated with multiple abortions is more uncertain.”

The report, which was published last week at the APA's annual conference in Boston, found evidence that women who had late abortions because of foetal abnormalities often suffered adverse psychological reactions, similar to those experienced by women who had miscarried or had a stillbirth. These effects, however, were seen among women who had lost a wanted pregnancy, and should not be extrapolated to those who chose to terminate for other reasons. They were also less serious than those seen in women who gave birth to infants with life-threatening defects.

The majority of UK abortions meet the criteria for which the APA said there are no attested psychiatric risks. About 90 per cent are conducted in the first trimester to end unwanted pregnancies, and two thirds of the abortions carried out in England and Wales last year were for women who had not had one before.

The results are significant, because after the defeat in May of attempts to reduce the 24-week time limit for terminations anti-abortion campaigners are now demanding mandatory psychiatric counselling and a “cooling-off period”.

Supporters pointed to research such as a New Zealand study led by David Ferguson, of Christchurch School of Medicine, which found in 2006 that women who had had abortions had an elevated risk of mental health problems. The study prompted a group of doctors led by Patricia Casey, of University College, Dublin, to write to The Times: “Since women having abortions can no longer be said to have a low risk of suffering from psychiatric conditions such as depression, doctors have a duty to advise about long-term adverse psychological consequences of abortion.”

In March, Nadine Dorries, the Conservative MP who led attempts to reduce the time limit to 20 weeks, said: “We now know that abortion leads to depression and mental health problems in later life, along with other complications in future pregnancies.”

The Ferguson study was among those whose design was criticised by the APA review, in this case because it did not distinguish between abortions of wanted and unwanted pregnancies.

The APA's conclusions matched those of the Commons Science and Technology Select Committee, which last year found no evidence for psychiatric damage caused by abortion. The Royal College of Psychiatrists also considered research inconclusive.

Ann Furedi, chief executive of the British Pregnancy Advisory Service, which provided 55,000 abortions in 2007, said: “Abortion research is highly politicised, but large, high-quality studies consistently show that having an abortion does not result in psychological damage.”

Mrs Dorries said: “If this rehashed, inconclusive and dated research is being used to deny women in the UK who seek an abortion the right to counselling, then it's a fairly desperate act on behalf of the abortion industry and those who wish to deny women the right to make a fully informed decision.”

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