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The rate of suicide attempts among US high school teens dropped in states which implemented same-sex marriage laws, a study has found.

Same-sex marriage policies were associated with a 7% fall in reported suicide attempts, according to analysis of 17 years of data.

The drop was particularly evident among "sexual minorities" - which saw a 14% drop in suicide attempts.

It concluded that same-sex marriage laws had "mental health consequences".

But the report also said it could not say exactly how policy on same-sex marriage reduces suicide attempts - just that there is evidence of an association.

Suicide is the second-largest cause of death among 15-24 year olds in the United States, according to the report's data.

About 29% of gay, lesbian, and bisexual high school students reported at least one suicide attempt in the 12 months before answering the survey - compared with just 6% of heterosexual teens.

Media playback is unsupported on your device Media caption The morning gay marriage came to the US

The new study compared the change in suicide rates from 32 states permitting same-sex marriage - before and after the policy was implemented - with 15 states which did not allow same-sex marriage.

The report's author, Julia Raifman, said the drop-off in suicide attempts, particularly among lesbian, gay, and bisexual teens, was interesting because "high school students are unlikely to marry in the immediate future - so that suggests that it's not a direct benefit from marriage."

"It's likely that something about having equal rights, or having more hope for the future, is driving the results," she said.

Media playback is unsupported on your device Media caption Family portraits of same-sex marriage couples

In an editorial accompanying the paper in the the Journal of the American Medical Association Paediatrics, Columbia University's Mark Hatzenbuehler wrote that "stigma is one of the most frequently hypothesised risk factors".

But, he wrote, research into stigma and mental health is almost exclusively at the personal level, rather than looking at factors in society at large.

"That literature has tended to overlook what we call structural forms of stigma - which include ... laws and policies," he said in an interview.

"Those results really highlight the fact that the legal climate surrounding LGB adolescents really deserves greater attention," he added.

The study analysed data on 762,678 teens from the Youth Risk Behaviour Surveillance System - a large-scale US-wide survey carried out every two years.

The report's data, however, depended on teens self-reporting a suicide attempt and found that there was "limited data" on sexual orientation. It also did not include suicidal actions which resulted in death.

The United States Supreme Court ruled that same-sex marriage was a right in every state in June 2015 - after the period covered by the new study.