In the past few years, public health experts have increasingly investigated the factors, such as mental illness or substance abuse, behind why teenagers attempt suicide. More recently, researchers from Johns Hopkins University and Harvard University asked a different sort of question: whether the legalization of same-sex marriage could have an impact on suicide attempts in adolescents.

Such an association seems to exist, at least based on self-reported data from more than 750,000 students. As the scientists wrote in JAMA Pediatrics on Monday, students living in states where same-sex marriage was legalized saw a drop in suicide rates, compared to students living elsewhere (a critical point being that the scientists investigated an association, not a causal relationship).

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The new study was not designed to explain why the drop occurred. But one possibility, the study authors said, was that same-sex marriage was related to a reduction in social stigma.

“Policymakers need to be aware that policies on sexual minority rights can have a real effect on the mental health of adolescents,” said Julia Raifman, a study author and an epidemiologist at the Johns Hopkins Bloomberg School of Public Health in Baltimore, in a news release. “We can all agree that reducing adolescent suicide attempts is a good thing, regardless of our political views.”

Psychiatrist Victor Schwartz, a medical officer at the youth suicide prevention group the JED Foundation, who was not involved in the study, said that feeling stigmatized can be frightening and painful. “It’s a real risk factor, a feeling that you’re at odds with your family or community,” he said to PBS. “You feel like you’re going to be left out on your own.”

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The Johns Hopkins and Harvard scientists relied on data from the Youth Risk Behavior Surveillance System, a biannual Centers for Disease Control and Prevention survey of high school students. The survey collects information about diet, sexual behaviors, and drug and alcohol use in U.S. high schoolers. Between 1991 and 2015, more than 3.8 million students responded to the survey.

The researchers examined the data from 762,678 students who answered the survey between 1999 until January 2015. (That is, before the Supreme Court decision in June 2015 that ruled same-sex marriage was a constitutional right that could not be denied across the U.S.) The data reflected 32 states that legalized same-sex marriage between 2004 and 2015, as well as the 15 states that did not.

One of the survey questions was this: “During the past 12 months, how many times did you actually attempt suicide?” Overall, 28.5 percent of students who identified as a sexual minority responded that they had attempted suicide one or more times. For heterosexual students, 6 percent responded they had attempted suicide.

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“It’s not easy to be an adolescent,” Raifman said, “and for adolescents who are just realizing they are sexual minorities, it can be even harder — that’s what the data on disparities affecting gay, lesbian, and bisexual adolescents tell us.”

The scientists compared rates before and after same-sex marriage legalization. After states legalized same-sex marriage, the number of self-reported suicide attempts also decreased. For all students surveyed, regardless of sexual orientation, the percentage of students who reported a suicide attempt dropped from 8.6 percent to 8.0 percent.

For gay, lesbian and bisexual students in particular, the decrease was more pronounced. Rates of suicide attempts decreased from 28.5 percent to 24.5 percent (a 14 percent reduction in suicide attempts). There was no change in states that did not legalize same-sex marriage before January 2015.

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Extrapolating that finding to all U.S. students, the study authors wrote, would equate to 134,000 fewer adolescents attempting suicide each year.

This finding supported the idea that stigma — involving loss of status, discrimination or stereotyping — may underlie some suicide attempts, public health experts said. “Stigma is one of the most frequently hypothesized risk factors for explaining sexual orientation disparities in suicide outcomes,” wrote Columbia University’s Mark L. Hatzenbuehler in a JAMA Pediatrics editorial accompanying the study.

Although the majority of high school students do not have immediate plans to get married, legalizing “same-sex marriage reduces structural stigma associated with sexual orientation,” Raifman said.

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“There may be something about having equal rights — even if they have no immediate plans to take advantage of them — that makes students feel less stigmatized and more hopeful for the future.”

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Correction: A previous version of this article described the Youth Risk Behavior Surveillance System survey as occurring annually. It is conducted every two years, not each year.