A large-scale study has confirmed that children who are raised by same-sex parents are just as happy as those raised in traditional families.
Researchers looked at 19,000 studies and articles on same-sex parenting from 1977 to 2013, and found that there were no differences in the psychological, behavioural or educational outcomes of children.
Co-author and University of Oregon sociology professor, Ryan Light, said: "Consensus is overwhelming in terms of there being no difference in children who are raised by same-sex or different-sex parents."
Light hopes the results of the research, titled “Scientific Consensus, the Law, and Same Sex Parenting Outcomes", will impact future cases in court regarding gay marriage.
The studies showed some disagreements on the outcomes of same-sex parenting in the 1980s, but a clear consensus had formed by 2000 that there was no difference between same-sex and different-sex parenting.
Light added: "Across the board we find there's no significant differences, and to our knowledge this is the most comprehensive analysis of this type on this issue."
Gary Gates, Research Director at the Williams Institute, UCLA School of Law, said he believes the argument that same-sex parents are less adequate than heterosexual parents has largely been taken out of the legal debates. But, he added, it's always possible that it could come up.
The results come as the US Supreme Court is set to rule by the end of this month on whether same-sex marriage is legal.
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In late 2014, a study of 500 children concluded children of gay parents are happier and healthier than their peers.
Conducted by Australia's University of Melbourne, the research showed children raised by same-sex couples scored 6% higher than the general population when it came to general health and family cohesion.
The lead author of the study, Dr Simon Crouch, said: "Because of the situation that same-sex families find themselves in, they are generally more willing to communicate and approach the issues that any child may face at school, like teasing or bullying."
Blogging on HuffPost UK Parents, Jane Newman wrote: "Why shouldn't a gay couple be allowed to have a family of their own?
"Surely a child with gay parents is better than a child with straight parents who argue constantly and end up getting divorced."