There is no credible evidence that women who terminate an unwanted first pregnancy are at a higher risk of depression, researchers say.
The study looked at women's pregnancy decisions
A recent US study had suggested having an abortion increased significantly a woman's chance of suffering depression.
But the authors of a British Medical Journal work looking at 1,247 women say pre-existing mental health might be a better predictor of depression risk.
Anti-abortion lobbyists maintain abortions are psychologically damaging.
The latest study looked at US women who aborted or delivered an unwanted pregnancy.
It showed that the women who opted for a termination reported less depression than those who chose to carry on with the unwanted pregnancy.
However, this might have been down to differences in education and income between the two groups, because the women who went for abortions tended to be more affluent than those who did not, it said.
They also tended to have fewer children already - large families have been linked to increased risk of depression before.
"This suggests that if the goal is to reduce women's risk of depression, research should focus on how to prevent and ameliorate the effect of unwanted childbearing, particularly for younger women," said the researchers.
Professor Nancy Russo, from Arizona State University, and her colleague Sarah Schmiege from the University of Colorado, said the difference between their results and the previous US study that did find a link between abortion and depression might be down to the way the studies were carried out.
In the previous study, the researchers looked at women with unintended pregnancies, which could have included some that were wanted although unplanned.
In the current study, Professor Russo made sure they only included women who said the pregnancy was unwanted.
The follow-up period between pregnancy and depression assessment ranged from four to 10 years.
About 30% of pregnancies in Britain are unplanned, it is estimated.
Last year, there were 185,400 abortions in England and Wales. Only 1% of the abortions, 1,900 in total, were carried out under grounds that the child would be born disabled.
Dr Michael Jarmulowicz, of The Guild of Catholic Doctors, questioned the latest study's findings.
He said the evidence suggesting that abortion increases the risk of suicide or self-harm attempts, as well as depression and a possible increased risk of death from all causes, was much stronger.
A spokesman from the Society for the Protection of Unborn Children said: "Our counselling service deals with many women who have had abortions, and their feelings of remorse and sorrow are 100% genuine and deeply painful.
"Even if abortion did no emotional or physical harm to women, it would still be wrong because it always takes an innocent, defenceless human life.
"We hope society will one day see abortion as the grave denial of a basic human right that it undoubtedly is."
Sophie Corlett, of the mental health charity Mind, said: "While any distressing life event has the potential to affect an individual person's mental health, this study supports earlier research that abortion, as opposed to bringing to term an unwanted pregnancy, does not increase the risk of later depression.
"Mind would welcome attention to the support needs and work/education opportunities for all women who experience unwanted pregnancies, whatever the outcome might be."
A spokeswoman from the British Pregnancy Advisory Service, which provides abortions to women in Britain, said: "From our experience, abortion does not cause depression, as long as a woman has discussed all her options and made a fully informed decision.
"Very few women return for post-abortion counselling and this is because they made the best decision for them at the time and see no need to talk to a counsellor."
Julia Millington of the ProLife Alliance said: "The problems that lead women to opt for abortion - financial hardship, abusive men, social stigma - are still not being properly addressed. Real 'choice' would give women the freedom and support to feel that abortion is neither the only nor good solution that the pro-abortion lobby suggests."