The big difference marriage equality could make to Australian's mental health.

Legalising same-sex marriage in Australia wouldn’t just benefit couples wanting to wed, it could help save lives, new research out of the US has shown.

It’s a long-held belief that stigma and social exclusion have a direct impact on the wellbeing of people within the LGBTI community, according to the Black Dog Institute.

A study published this week backs up this belief and shows that creating a more inclusive society for young people to live in could improve their mental health and happiness.

Listen: Senator Penny Wong talks about same sex marriage.

The study compared suicide attempt rates across public high schools in the 32 US states that allow same-sex marriage, before and after it was legalised.

Researchers measured a significant difference in the number of suicide attempts when marriage equality was introduced. It found seven percent fewer students reported a suicide attempt.

Black Dog Institute senior researcher Dr Fiona Shand said the findings of the study, which collected data from 750,000 adolescents, was solid data that legalising same-sex marriage equality would reduce suicide.

"We know that marriage, regardless of the sexual orientation of the partners, is strongly associated with physical and mental health benefits and a lower suicide risk," Dr Shand said.

"This research provides evidence that same-sex marriage is an important strategy for improving the mental health of the LGBTI community in Australia and reducing the overall suicide rate."

It's not just that inclusion would be beneficial to those who identify as gay, lesbian, bisexual, transgender or intersex, it's that doing nothing could be harmful.

A statement published by the Royal Australian and New Zealand College of Psychiatrists in April last year called for marriage equality on health grounds.

"Evidence shows that discrimination and marginalisation experienced by the LGBTI population increases the risk of developing mental health issues, and also creates barriers to accessing supportive services," the statement read.

Meanwhile, Black Dog Institute Director Prof Helen Christensen said that more research was also needed to determine which types of interventions would reduce discrimination and stigma.

If you're struggling with your mental health, or know someone who is, please call Lifeline on 13 11 14.