No high-quality study done to date can document that having an abortion causes psychological distress, or a “post-abortion syndrome,” and efforts to show it does occur appear to be politically motivated, U.S. researchers said on Thursday.

A team at Johns Hopkins University in Baltimore reviewed 21 studies involving more than 150,000 women and found the high-quality studies showed no significant differences in long-term mental health between women who choose to abort a pregnancy and others.

“The best research does not support the existence of a ‘post-abortion syndrome’ similar to post-traumatic stress disorder,” Dr. Robert Blum, who led the study published in the journal Contraception, said in a statement.

“Based on the best available evidence, emotional harm should not be a factor in abortion policy. If the goal is to help women, program and policy decisions should not distort science to advance political agendas,” added Vignetta Charles, a researcher and doctoral student at Johns Hopkins who worked on the study.

An estimated 1.29 million American women get elective abortions each year, according to the U.S. Centers for Disease Control and Prevention. An estimated 25 million women globally have legal abortions every year.

Abortion is a hot-button political issue, with many voters and members of the U.S. Congress as well as state lawmakers seeking to ban it.

“The U.S. Supreme Court, while noting that ‘we find no reliable data to measure the phenomenon,’ cited adverse mental health outcomes for women as part of the rationale for limiting late term abortions,” Blum’s team wrote.

The researchers reviewed all English-language, peer-reviewed publications between 1989 and 2008 that studied relationships between abortion and long-term mental health.

They analyzed those that included valid mental health measures and factored in pre-existing mental health status and potentially confusing factors.

“The best quality studies indicate no significant differences in long-term mental health between women in the United States who choose to terminate a pregnancy and those who do not,” they wrote.

“...studies with the most flawed methodology consistently found negative mental health consequences of abortion,” they added. “Scientists are still conducting research to answer politically motivated questions.”

WASHINGTON (Reuters)