DEPRESSED women have more sex than those who are happier, regardless of whether they are in a relationship or not, a study of Australians has found.

A survey of Melbourne women presented at an international mental health conference has concluded that females who suffer from mild to moderate depression have a third more sexual activity than those who are not.

They also had more sexually liberated attitudes, a bigger variety of sexual experiences and, if single, were more likely to partake in casual sex, Dr Sabura Allen, a clinical psychologist at Monash University, said.

"It was more sex and more of everything from kissing to petting, foreplay and intercourse," said Dr Allen, who studied the recent sexual experiences of 107 depressed and non-depressed women who were in relationships.

"We knew this anecdotally from clinical samples but this is the first time it's been shown in research."

She said depressed women were likely seeking out sexual intimacy more often to help feel more secure.

"When people are depressed they feel more insecure about their relationships and concerned that their partner may not care about them or find them valuable," Dr Allen said.

"Having sex helps them feel that closeness and security."

Asked whether intercourse could be an effective balm for depression, the psychologist said "we really don't know but we presume it helps as it gives these women opportunities to be close to their partner and loved."

The team also is investigating depressed single women and has found a trend towards more casual sex than happier singles.

Dr Allen said Australian couples tend to have sex between once and three times a week, with "very much the majority in the once a week group".

Single women have it "significantly less", but the same is not necessarily true of single men.

The study, soon to be published in a British medical journal, was presented today at the International Congress on Women's Mental Health in Melbourne where the latest research in mental illness and hormone-related conditions is being showcased.

New studies have shown high rates of severe PMS and post-natal depression among Australian women, a dramatic drop in the abortion rate, and a promising new treatment for Alzheimer's disease.