Any time I met a guy who didn’t respond to me sexually, it would make me determined to have him,” confesses Valerie, 35, a human-resources manager in the City. “It became a challenge, a game, regardless of whether he was married or with someone. The lowest point came when I tried to seduce my best friend’s fiancé. I couldn’t bear the fact that, when they were together, he wouldn’t so much as look at me. It was an itch I had to scratch.”

“Sex addict” is the last phrase that would come to mind if you met the demure and sober-suited Valerie. Yet she is in 12-step recovery for that very issue. “Everyone used to tell me how lucky I was, as I could get any man I wanted. I’m quite a competitive person and it was important for me to know that, in my circle of girlfriends, I was viewed as the hottest.”

That sex and, by extension, love are highly addictive is no longer up for debate. Comparative brain scans of the love-struck and cocaine-addicted show almost identical areas of brain activity. And, for the first time, people are starting to talk about sex addiction. Russell Brand has owned up to having treatment and David Duchovny recently outed himself as a sufferer. Next month sees the release of a Hollywood film, Choke, devoted to the subject.

Experts say the number of sex addicts is rising — and, contrary to popular opinion, they are not all men. “In America, 30% of people coming in for treatment for sex addiction are female,” says Don Serratt, director of Life Works, which offers sex-addiction treatment in the UK. In this country, few women present themselves as sex addicts, but that doesn’t mean the problem is less prevalent. “They’ll come for help with alcoholism, drug addiction or depression and, in the course of treatment, the sex addiction, the root cause of the other addictions, will be uncovered,” Serratt says.

Valerie was unaware she had an addiction, even when her friend’s fiancé rejected her advances and threw a drink over her, telling her some unpleasant home truths for good measure. It was only as she got older and her friends started to settle down that she began to question her behaviour.

“I was embarrassed to find myself aged 35, with the longest relationship on my romantic CV lasting only three months,” she says. She went to counselling because she wanted to stop going for the wrong men. “That’s when I realised that I’d been living in a fantasy world. What I loved most about sex wasn’t the act itself. It was lying in bed together afterwards, talking into the small hours, feeling that sense of connection. I often convinced myself I was in love with these guys, but it would soon wear off.”

Susan Cheever, a self-confessed sex addict who has just written Desire: Where Sex Meets Addiction (Simon & Schuster), agrees that this blurring of the lines between the compulsions of love and sex is common among women. “If there is a difference between sex and love addiction, I don’t know what it is,” she says. “Sometimes people say they just fall in love too frequently. Are they saying they don’t want to have sex with those people? Love addict sounds nicer for sure.”

As Cheever recounts in the book, there were times when every man who crossed her path was fresh prey, from removal men to bookshop reps — taking in three husbands and her mother’s oncologist on the way. “Whenever there was a crisis,” she admits, “I found a man to take the edge off the feelings of helplessness and pain” — regardless of the upheaval she risked unleashing on her husbands and two children. “Adultery is the drink-driving of sex addiction,” she observes.

A bleaker story emerges, however. “My parents spent a great deal of time telling me that I was unattractive and would never find a husband. Perhaps proving my parents wrong was one of my motivations. If so, I didn’t realise it at the time. It’s tricky, because addiction to other people, specifically addiction to a sex partner, is the only one that is applauded and embraced by our culture, despite the fact that there is more collateral damage than with drugs or alcohol.”

It is a pattern Serratt is all too familiar with. “Female sex addicts crave intimacy, ” he says. “They’ll use sex and seduction to create that closeness with a guy — but, once they get it, they freak out and move on to the next one.”

Yet, although they crave intimacy, Serratt believes female sex addicts are subconsciously terrified by it. Because of their low self-esteem, they are scared of a man getting to know the “real” them. “Sex addicts will often say, ‘Oh, I can never meet the right man’, but that’s because as soon as a guy turns up who is everything they want, it scares them and they kill it. Once they’re in a relationship, they’ll begin to find fault and start saying ‘Oh, he’s lazy/he’s fat/he’s broke’, then dump him. Sex addicts also have poor discernment skills for choosing boyfriends. They tend to go for superficial qualities, because what they’re attracted to is a fantasy.”

Certainly for Justine, a 38-year-old mother of two, fantasy was the driving force behind a habit that nearly wrecked her life. She was married to a rich entrepreneur for 18 years, and her life appeared enviable, yet for two decades she had a string of affairs, taking crazy risks to spend time with her lovers.

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