It is discrimination, not same-sex parents, that harms children, according to a leading group of Australian paediatricians.

In a comprehensive review published today in the Medical Journal of Australia, 13 child and adolescent health experts from the Melbourne Children's found children raised in families with same-sex parents do "as well emotionally, socially and educationally" as children raised by heterosexual parents.

"The consensus of the research — pretty clearly, over several generations — is that children of same-sex parents do as well, if not better, than those children raised by heterosexual parents," said senior author Professor Frank Oberklaid of the Murdoch Children's Research Institute.

As the same-sex marriage postal survey voting period enters its final weeks, the review addresses one of the key claims of the 'No' campaign — that children do better when raised by a mother and a father.

The child health experts said this is "misinformation".

They argue the "homophobic campaign messages" associated with the same-sex marriage debate pose an increased mental health risk for the LGBTIQ community, including children of same-sex couples, and LGBTIQ young people.

"The negative and discriminatory rhetoric of the current same-sex marriage debate is damaging the most vulnerable members of our community — children and adolescents.

"It is essential that we recognise the potential for the debate about marriage equality to cause harm," Professor Oberklaid said.

What does the research say?

Professor Oberklaid and his colleagues analysed four major reviews and meta-analyses spanning three decades of peer-reviewed research.

A 2017 review of 79 studies concluded "an overwhelming scholarly consensus ... that having a gay or lesbian parent does not harm children"

A 2017 review of 79 studies concluded "an overwhelming scholarly consensus ... that having a gay or lesbian parent does not harm children" A 2014 review of over 40 studies concluded children of same-sex couples do as well as other children across a range of measures including academic, social, cognitive and psychological health

A 2014 review of over 40 studies concluded children of same-sex couples do as well as other children across a range of measures including academic, social, cognitive and psychological health A 2013 review of the Australian and international research found "being raised by same-sex parents does not harm children"

A 2013 review of the Australian and international research found "being raised by same-sex parents does not harm children" A 2010 meta-analysis of 33 studies found parents' gender or sexuality does not adversely affect child health or wellbeing

They found "family processes", such as parenting quality and parental wellbeing, rather than "family structure", the number, gender, or sexuality of parents, make "a more meaningful difference to children's wellbeing and positive development".

"Things like the quality of parenting, parental wellbeing, the way parents relate to the child, the nurturing and stimulating qualities in the home … those factors are much more important than whether the parents are heterosexuals or same sex," Professor Oberklaid said.

Associate Professor Kylie Gray from the Centre for Developmental Psychiatry and Psychology at Monash University agreed, and said there was a strong body of international research to demonstrate that quality parenting and a nurturing family environment were key to children's wellbeing and development.

"These are the factors that are important for raising healthy and resilient children," she said.

The authors also highlighted that there is some research to suggest children with same-sex parents "do better" in some areas than other children.

"In addition to equivalent social and educational outcomes, these studies conclude that children raised by same-sex couples show better psychological adjustment, and greater open-mindedness towards sexual, gender and family diversity."

They noted, however, that these positive differences may reflect the parenting, socio-economic status and family stability within the same-sex parented families studied.

"Because it's quite difficult to form a family as a same-sex couple, and you often have to go through IVF and fertility treatment pathways, the cohort tends to be slightly better educated, with slightly higher income," said Dr Simon Crouch, the lead investigator of the Australian Study of Child Health in Same-Sex Families.

"These are factors that play a role in better child health and wellbeing."

Impact of stigma and discrimination

However, same-sex couples and their families face "devaluing and discriminatory" messages regarding LGBTIQ issues and this can have negative psychological impacts, the review found.

"Children and adolescents with same-sex parents are emotionally affected when they and their families are exposed to homophobia, discrimination, prejudice and social stigma," the authors wrote.

Professor Oberklaid said the effect on children could be both direct and indirect.

"We found that same-sex couples who are subject to discrimination ... they're affected, they experience anxiety, and that's not good for children.

"We also found that children raised in same-sex parent families worry about being teased or bullied by their peers, particularly in the school environment.

"As a result, they feel distressed and guilt and a sense of shame, and this is harmful to their wellbeing and sense of self, much more than the actual raising in the families."

Associate Professor Gray said discrimination of any kind is damaging to children's emotional wellbeing and development.

"It's not just about family structure or the gender of you parents, any kind of discrimination is harmful."

The review also found LGBTIQ young people were at risk during the debate.

"Young LGBTIQ people are much more likely to experience poor mental health, self-harm and suicide than other young people," Professor Oberklaid said.

"Sadly, this is largely attributed to the harassment, stigma and discrimination they and other LGBTIQ individuals and communities face in our society."

Debunking previous research

A number of studies have found children with same-sex parents have poorer outcomes than children with heterosexual parents.

The often-cited Regnerus study analysed survey data from adults aged 18-39 years and concluded that those with a gay or lesbian parent fared worse on a range of social, emotional and relational outcomes when compared with adults raised by heterosexual, married, biological parents.

However, this and other studies that report poor outcomes have been widely criticised for their methodological limitations, the authors wrote.

"The Regnerus study compared adults raised by a gay or lesbian parent in any family configuration with adults who were raised in stable, heterosexual, two-parent family environments," the review stated.

"When re-analysed, taking family stability and having two active parents into account, the data showed that outcomes were similar for adults regardless of their parents' sexuality."

Dr Crouch said it was important to look at the whole collection of research to get a clear understanding of what's going on.

"The significant weight of the evidence in this particular area of research is that children with same-sex parents — when all other confounders are taken into consideration — are doing just as well as children from other backgrounds."

Professor Oberklaid acknowledged "no research is without its issues", and said there were methodological challenges in answering questions about children's wellbeing in same-sex parented families.

"Samples of children with same-sex parents tend to be small… This means that much of the research on same-sex parented families has used convenience or volunteer samples that can be biased," the review read.

'We need to speak up'

Children and adolescents with same-sex parents are "doing well", researchers said, despite the discrimination that their families endure.

"This will not continue for long in the face of hostile debate," they wrote.

They said doctors have a duty of care to all groups in society, particularly to those who are vulnerable.

"As paediatricians, we have a responsibility to protect children. If children are being hurt by these sorts of claims, we believe we have a duty to speak up," Professor Oberklaid said.

The authors of the review include experts from the Murdoch Children's Research Institute, University of Melbourne, Royal Children's Hospital, Victorian Clinical Genetics Services, Children's Hospital at Westmead, and the Liggins Institute at the University of Auckland.