Using hormonal birth control has been linked in the past to an increased risk of depression in women. But new research, published in the journal Contraception, is questioning that association: it found no link between certain types of birth control and depression.

Researchers from Ohio State Wexner Medical Center reviewed 26 studies, including five randomized controlled trials, on the risk for depression from progestin-only contraception. The review included a variety of methods including birth control pills, injections and implants like the intrauterine device (IUD).

Lead study author Dr. Brett Worly, an OB/GYN at the medical center, says he wanted to do the study after hearing questions from female patients about the potential risks for depression from birth control. He and his colleagues found no connection from their review.

Some studies in the past have linked contraception to a higher depression risk, but Worly says his research shows that the most high-quality and extensive studies do not. “We wanted to look at the best scientific evidence and see where it was pointing to,” he says. “It looks like there’s no link and no causation. There are some voices that say there could be, but our best available evidence shows there isn’t a link.”

Even when the researchers looked at higher-risk groups, like women who were already depressed, they did not find evidence that the contraception caused depression or made it worse. “I think this study should reassure [women] that they shouldn’t experience depression as a direct result of their contraception,” he says.

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In a 2016 study, Worly and his colleagues did a similar review of all studies looking at the link between combined hormonal contraception—including birth control pills with both estrogen and progestin—and depression and similarly found that, based on available data, most women don’t appear to have any mood-related problems due to their birth control.

However, like many drugs, birth control is known to cause side effects, and depression is often listed as one. A different widely covered study in 2016 found that women using hormonal birth control had a 40% higher risk of depression after six months compared to women not using hormonal birth control. But that study did not prove causation. Worly says the fact that depression is so common—even more so among women than men—can make it more difficult to tease apart a real phenomenon.

“It’s confusing, because even though it’s not talked about, depression is really common and can develop for all sorts of reasons,” he says. “While some women will develop depression [when using birth control], as far as I can tell, it doesn’t seem like one causes the other, but it’s more happenstance.”

More research is needed, and even Worly acknowledges that though his study may be one of the most extensive, it may not be the final say. In this study, the researchers only looked at diagnosed depression and not other factors, like depressive symptoms or mood changes. Women should talk to their physicians about their concerns with their birth control.

“We used the best evidence, but there’s still room for it to get better,” he says. “While this is the best answer we have right now, there’s room for better and different answers to come. This isn’t necessarily the end of the conversation.”

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