The Scottish Catholic Church has argued against equal marriage rights for same-sex couples, saying “exceptionally hazardous” gay relationships lead to shorter life expectancies.

It relied on a study discredited by its own authors for this purpose ten years ago and a paper authored by the founder of the Family Research Institute, which is designated a “hate group” in the US by the Southern Poverty Law Center.

At an anti-gay marriage rally for Scotland for Marriage in November, Cardinal O’Brien, the leader of the Roman Catholic Church in Scotland said: “At the heart of this debate [...] there is one perspective which seems to be completely lost or ignored, it is the point of view of the child.

“All children deserve to begin life with a mother and father, the evidence in favour of the stability and well being which this provides is overwhelming and unequivocal.”

At the time, PinkNews.co.uk asked the Scottish Catholic Media Office, the press service of the Bishops’ Conference of Scotland, to substantiate its claim of “overwhelming evidence”.

In response, the Church provided a 2005 report by the Institute for American Values in New York, which makes 26 conclusions about the importance of marriage in modern society, along with two scientific studies which, it says, show gay people to have “unstable” and “medically exceptionally hazardous” relationships.

None of the conclusions in the Institute for American Values report are obviously inapplicable to same-sex marriages, an issue it does not explicitly address.

But the Church spokesperson said there is “much research on reduced lifespan among homosexuals” and offered two studies as examples.

The first, “Modeling the impact of HIV Disease on Mortality in Gay and Bisexual Men”, by Robert Hogg et al., was published in 1997 in the International Journal of Epidemiology.

Using data it collected from 1987 to 1992, it determined the life expectancy of gay men in a Canadian city at that time to be up to 20 years shorter than the average for all men.

But in 2001, the study authors said the findings should not be used to infer anything about gay men’s life expectancy in general outside that 5-year period.

The statement came after they were told the paper was being used for political purposes.

They wrote in the same journal: “From these reports it appears that our research is being used by select groups in US and Finland to suggest that gay and bisexual men live an unhealthy lifestyle that is destructive to themselves and to others.

“These homophobic groups appear more interested in restricting the human rights of gay and bisexuals rather than promoting their health and well being.

“The aim of our research was never to spread more homophobia, but to demonstrate to an international audience how the life expectancy of gay and bisexual men can be estimated from limited vital statistics data.”

The findings, according to Hogg et al., would not have been accurate even ten years ago due to the speed of advances in medical care for those living with HIV.

They said: “If we were to repeat this analysis today [in 2001] the life expectancy of gay and bisexual men would be greatly improved. Deaths from HIV infection have declined dramatically in this population since 1996.”

According to research in the British Medical Journal, a person living with HIV who begins treatment with a CD4 count of 350 cells/mm3 can expect to live to 75 years of age, compared with the UN’s figure of 79.4 years for all UK citizens at birth.

The 1997 study authors concluded: “The aim of our work was to assist health planners with the means of estimating the impact of HIV infection on groups, like gay and bisexual men, not necessarily captured by vital statistics data and not to hinder the rights of these groups worldwide.

“Overall, we do not condone the use of our research in a manner that restricts the political or human rights of gay and bisexual men or any other group.”

The second piece of research, “Does Homosexual Activity Shorten Life?”, was authored by Paul Cameron, founder of the Family Research Institute, and published in Psychological Reports, a journal which reportedly charges authors to publish their work.

The mission statement of the Family Research Institute, which Cameron founded as the Institute for the Scientific Investigation of Sexuality and still runs, is “to generate empirical research on issues that threaten the traditional family, particularly homosexuality, AIDS, sexual social policy, and drug abuse.”

It is officially classed as a hate group by the Southern Poverty Law Center alongside the Westboro Baptist Church.

The Church spokesperson told PinkNews.co.uk the 1998 study shows “homosexual activity may be associated with a lifespan shortened by 20 to 30 years”.

Cameron’s scientific work has been heavily criticised. The American Psychological Association, the American Sociological Association and the Canadian Psychological Association have all officially distanced themselves from him.

In 2010, he released a study which said gays in the military were four to seven times more likely to rape a fellow serviceman than straight men were to rape servicewomen.

The Church spokesperson told PinkNews.co.uk many “pro homosexual campaigners” believe Cameron’s methodology is “at best unsound”.

But appearing to compare homosexuality to an addiction to tobacco, he added: “The (US) National Cancer Institute says smoking takes from 7 to 10 years off someone’s life, smoking advocates have also questioned the methodology involved.”

Cameron was tricked into appearing in the 2009 ‘mockumentary’ Brüno by Sacha Baron Cohen, in which he gave the title character advice on how he may be able to turn straight by suggesting he give women “a chance to seduce [him]“.

The Scottish Roman Catholic Church helped deliver 20,000 postcards to the Scottish Parliament last month in opposition to proposals which would allow gay couples the right to marry, and have taken out adverts publicly opposing the move.

The Church spokesperson concluded: “Christians should always be driven by compassion and love for their fellow human beings and as a result try to urge them away from the path they are on and encourage society away from facilitating any type of hazardous behaviour not because we DON’T care for them, but precisely because we DO.

“Christians’ concern therefore should be at a far deeper level than the thoughtless ‘do as you please’ platitudes of the politically correct secular humanists.”