A 17-year study into families headed by lesbian parents has found that their children have fewer behavioural problems, get better results and are more psychologically sound than children brought up by straight parents.

Researchers at the University of California followed 78 children born to lesbian mothers from birth to the age of 17.

They also found the children were less likely than those with straight parents to behave aggressively or break rules.

The mothers were asked to rate their children on their behaviour, aggression and school marks, while the teenagers were rated with the Child Behavior Checklist, a standardised assessment. Each teenager also filled out an internet-based psychological questionnaire.

Study leader Nanette Gartrell said: ”Contrary to assertions from people opposed to same-sex parenting, we found that the 17-year-olds scored higher in psychological adjustment in areas of competency and lower in problem behaviours than the normative age-matched sample of kids raised in traditional families with a mum and a dad.”

“These are not accidental children,” she told WebMD Health News. “The mums tended to be older and attended parenting classes. They were very involved in the process of education [for their children].”

”They anticipated their kids would experience stigmatisation.”

The study did find that children who experienced homophobia had higher levels of depression and anxiety.

Knowing their biological father made no impact on children’s happiness and behaviour.

A number of previous studies have found that children of gay and lesbian parents are as happy, or happier, than their peers brought up by straight parents.

Last year, a study of 1,384 couples, 155 of whom were gay, found that as parents, their sexuality made “no significant difference” on the levels of emotional problems experienced by their children.

The Adoption and Children Act, which came into force in December 2005, gave gay couples and unmarried straight couples the right to jointly adopt children.

Lesbians undergoing IVF treatment can now record their partner as the second parent on the birth certificate.