A new study by researchers from the University of British Columbia has found a correlation between using oral contraceptives—also known as birth control pills—during adolescence and developing depression in adulthood.

The study, which was published in the Journal of Child Psychology and Psychiatry, examined the survey data of 1,236 women who filled out the U.S. National Health and Nutrition Survey.

The researchers looked at the prevalence of depression among three groups of respondents: women who started using oral contraceptives when they were 19 or younger, women who started using them during adulthood, and women who have never used them.

Between these groups, women who started taking oral contraceptives in adolescence were between 1.7 to three times more likely to develop major depressive disorder in adulthood.

However, the study only detected a stronger likelihood in developing depression within this group. It doesn’t state that there is a causal relationship between adolescent oral contraceptive use and depression in adulthood.

However, it does suggest a need for further research to determine if such a causal relationship exists.

“Millions of women worldwide use oral contraceptives, and they are particularly popular among teenagers,” UBC associate professor of psychology Frances Chen said in a media release.

“While we strongly believe that providing women of all ages with access to effective methods of birth control is and should continue to be a major global health priority, we hope that our findings will promote more research on this topic, as well as more informed dialogue and decision-making about the prescription of hormonal birth control to adolescents.”

Chen was the study’s senior author, while UBC psychology postdoctoral fellow Christine Anderl was the lead author.

Depression is the leading cause of suicide and disability deaths throughout the world, and women are twice more likely than men to develop it. Among women surveyed in the USNHNS survey, 45 percent used oral contraceptives for the first time between the ages of 15 and 19.

The study’s literature review notes that other research has found similar connections between oral contraceptive use and depression. A study in Denmark from 2016 of over one million women found that oral contraceptives were linked with higher rates of antidepressant usage and first-time depression diagnoses, with the strongest correlation being observed among adolescents.

Likewise, another large-scale study from Sweden found that among women who had taken oral contraceptives, adolescents were more likely than young adults to take medications for mental health purposes.

Since oral contraceptive pills alter someone’s sex hormones to prevent their ovaries from releasing eggs, the study’s authors pondered if this could have an adverse effect on a young person’s cognitive development.

“Adolescence is an important period for brain development,” said Anderl in a media release. “Previous animal studies have found that manipulating sex hormones, especially during important phases of brain development, can influence later behaviour in a way that is irreversible.”

The study also made sure to control for other factors that could explain the link between oral contraceptive use and depression. They include the age at which someone becomes sexually active, the age when menstruation begins, and whether or not someone was currently using oral contraceptives. The authors state that these factors did not account for their results.