OPINION: DEBATES ABOUT who should and should not be allowed to parent children must be informed by solid scientific evidence about what actually happens to children in these circumstances, rather than by unfounded assumptions and beliefs about the outcomes for children with lesbian or gay parents, writes Susan Golombok.
The question of whether children raised by lesbian and gay parents experience psychological harm is one that has arisen under different guises over the past 30 years.
Same-sex parents, in the form of lesbian mothers, first entered public consciousness in the UK in 1978 when an article in a London newspaper exposed a doctor who was helping lesbian women to become pregnant through donor insemination.
At the same time, lesbian women were beginning to fight for custody of their children when they divorced. Without exception, they lost the custody battle to the father on the grounds that it was not in their children's best interest to remain with their lesbian mother.
The concerns were twofold: firstly, that the children would be teased and bullied by their peers and would suffer psychological problems as a result and, secondly, that the boys would be less masculine and the girls less feminine than children from traditional families.
In the absence of any information at that time on the development and wellbeing of children raised by lesbian parents, a number of studies were initiated by university departments in the US and the UK.
The findings of these studies were strikingly consistent: children in lesbian families were no more likely to have psychological problems or to behave in ways that were atypical for boys or girls than children from traditional families.
Other studies over the years have come to the same conclusions and have been published in the most respected scientific journals in the field of child development. It is now widely accepted by academics around the world that, of the many reasons why children develop emotional or behavioural problems, the sexual orientation of their parents does not appear to be one.
Instead, what seems to matter most for children's healthy psychological development in families with same-sex parents is the same as in families headed by heterosexual parents - warmth and security in combination with an appropriate level of discipline and control.
Whether parents are heterosexual or homosexual, hostility and conflict between them, psychiatric problems and an impoverished social environment are major factors in the onset of psychological problems in children. These adverse circumstances are no more likely to arise in families headed by same-sex parents than by opposite-sex parents.
Since the 1970s, attention on same-sex parenting has shifted from custody battles to fostering and adoption, to access to assisted reproduction, and to same-sex marriage and civil partnerships.
In many parts of the world, a lesbian or gay sexual orientation is no longer considered to be a valid reason to deny men and women the right to raise a child.
While these are ultimately moral and social issues rather than psychological ones, it is essential that debates about who should be allowed to parent children are informed by solid scientific evidence about what happens to children in these circumstances. They should not be based on unfounded assumptions about the outcomes for children with lesbian or gay parents or, worse still, morally suspect distortions of such scientific evidence by those with an axe to grind.
Children today are being raised in families of all shapes and sizes, and what we are learning from investigations of these new family forms is that the structure of the family is less important for children's adjustment than the quality of family life.
Prof Susan Golombok is director of the centre for family research at the University of Cambridge. She has written more than 140 academic papers and authored or co-authored 15 books, including Growing up in a Lesbian Family (1997) and Parenting: What Really Counts (2000).
Prof Golombok is in Dublin today to participate in the British Psychological Society annual conference at the Royal Dublin Society.