With the authorisation of an unnecessary postal vote on marriage equality, the public debate has predictably turned into a circus. So it should perhaps come as no surprise that the intellectual equivalent of custard pies are being thrown. False claims by the no campaign that marriage equality would somehow constitute an attack on freedom of speech and set in motion a chain of events culminating in young boys having to wear dresses in schools are as imaginative as they are inaccurate.

The question would perhaps better be phrased as follows: does Australia wish to stop senselessly discriminating against a minority group, or not? Despite the prime minister declaring that he has more important things to focus on than this issue, a yes vote is vitally important for the sake of equal rights as well as the message of acceptance it would send to LGBT people in Australia.

Australia, like every other country in the world, has a long tradition of discrimination against people based on their sexual orientation, the mental health effects of which are striking. Gay men and women have higher rates of a range of mental health problems including depression, anxiety disorders, substance abuse problems and suicidal thoughts and behaviour. These rates apply to young LGBT people too – who are more than three times as likely to have attempted suicide than their heterosexual peers.

These higher rates of psychological distress and mental illness have been well explained by “minority stress” theory. Initially described in relation to the gay community, it could reasonably be applied to any minority group facing discrimination. The theory proposes that LGBT individuals are a disadvantaged minority group and face three additional types of stress not experienced by the majority: the objective experience of homophobic abuse, both physical and verbal; “perceived stigma” or the expectation of discrimination, which leaves people in a state of high alert and slowly chips away at their psychological defences; and the internalisation of negative attitudes or “internalised homophobia”, referring to LGBT people absorbing the negative attitudes around them which tragically fosters a misguided self-perception of inferiority.

Subsequent research has bolstered support for the minority stress theory, linking the three ingredients of this toxic cocktail to high levels of distress and suicidal thoughts and behaviour. So it is clear as day that stigma and prejudice are compromising the mental health of LGBT Australians.

It is fair to then ask whether or not marriage equality is the antidote to this problem, since it would not necessarily eradicate stigma and prejudice against LGBT people. We can, in fact, confidently say it would have a positive effect on their mental health – an American study found a significant reduction in mental health care visits and costs for gay men in the year after legalisation of same-sex marriage when compared with the 12 months prior. This was true for single men as well as those in a relationship, suggesting it may be the principle of acceptance rather than the actual ability to marry that makes a difference.

Conversely, another study found that US states banning same-sex marriage saw a rise in the number of various psychiatric conditions, with nearly 3.5 times the prevalence of generalised anxiety disorder. So the connection between marriage equality and better mental health in the LGBT community is also clear.

As well as being an equal rights issue, this is a public health issue, as matters of equality often are. One of the primary functions of any nation is to protect and enhance the wellbeing of its citizens. Since the institution of marriage is seen by many as a recognition by the state of the love and commitment between two people, excluding LGBT individuals from such an important rite of passage is discriminatory and perhaps even abusive. The clear evidence of the mental health ill-effects of discrimination against LGBT people should firmly banish outdated policies to the past where they belong.

Governments are not the only institution guilty of stigmatising LGBT people, of course – my own profession of psychiatry also has a shameful history of systematic discrimination against them, with homosexuality classed as a psychiatric disorder until as late as 1973. Psychiatry was criminally slow in realising the distress associated with being gay was caused by societal attitudes. Now that we have this understanding it would be criminal to disregard it and to continue exposing LGBT people to damaging prejudice when marriage equality provides a clear path to changing attitudes and improving LGBT mental health.

Kamran Ahmed is a psychiatrist and film-maker, writing on mental health, culture, politics and healthcare