According to Vrangalova "This study seems to suggest that casual sex can be a good thing for people who are open to it, desire it, and have positive attitudes towards it." But she added that safe sex and not being "too drunk" could be key to not regretting a one-night stand. Check out her interesting TEDex video – Is Casual Sex Bad For You? – which was published last month.

Dr Vrangalova, who is now adjunct professor at the New York University psychology department, decided to set up the Casual Sex Project to learn more about hooking-up. The project is a website where participants can share true stories of casual sex experiences of all kinds – one-night stands, short flings, sex buddies, friends-with-benefits, etc – as long as sex is involved with someone they are not in a serious relationship with. She hopes the project will not only encourage sexually expressive people to reveal their erotic secrets, but will provide people who don't choose to engage in casual sex with an insight into a more sexually fluid world.

It's not much different in Australia where casual sex has also become the norm among both young and older people. The young are experimenting and many older people who have separated or divorced are wanting to enjoy life for a while. The many dating websites are proof of this.

One of my clients had been in a serious relationship for five years with a partner who was her first lover. When they split up and she moved out she didn't want a new boyfriend again. She wasn't ready yet and she wanted to enjoy being single for a while and have casual sex. She saw me just for one session to get some "sex education" as she felt quite insecure.

Some people believe casual sex relationships are easy and have no complications, but sex is loaded with emotions and often you can receive mixed messages, especially after having sex which leaves you ecstatic for days. This can be a problem if the partner is not interested in romance or commitment. It's really important to set strict rules before starting a casual relationship to avoid disappointment and heartache. Another important issue is alcohol – often people regret or feel guilty about a sexual encounter after drinking too much – or not using a condom.