As a society, we used to be hung up on sex. Sex was a mark of how successful we were as human beings; it defined the way we dressed and how we were portrayed (think of the alpha-female, sexual-predator type of woman in car adverts). But as if to confirm that this chapter is coming to an end, a growing number of people have completely opted out of the sexual arena. There is a small but increasingly vocal minority of men and women who have never wanted to have sex with anyone. Researchers have only recently noticed a previously overlooked nugget in a 1994 survey of Britain’s sexual habits. Of the 8,000 people surveyed, 1% claimed they had never felt sexually attracted to anyone — in the UK as a whole, that amounts to about half a million people.

These people are now so open about what they describe as their asexuality, that there is even a website (www.asexuality.org) devoted to them, with a forum in which they cheerfully discuss their lack of desire and their irritation at the view that they must all be sick, lonely or desperate. They include women such as Paula Kripps, who is fit, healthy and in her thirties. “I have a nonexistent sex drive,” she says. “I have no physical or mental illness. I’ve just never been interested in sex. But that doesn’t mean I need a cure or a treatment — as far as I’m concerned, I’m normal.”

But can a nonexistent sex drive be described as totally normal? After all, isn’t sex a biological imperative, like eating? “Sex drive is a very variable thing,” says the psychologist Phillip Hodson. “There are a few utterly normal folk who never want much — if any — sex, and also a few utterly normal folk who want sex 15 times a day. Most of the rest fall somewhere between the two.”

However, asexuality doesn’t necessarily mean having no sex drive. The Asexual Visibility and Education Network (Aven) defines asexuals as those who never feel the desire to commit to having sex with others. While some never experience sexual desire at all, others feel aroused from time to time — sometimes to their irritation — but simply don’t want to have sex with other people.

This does not mean that they are lifelong loners or virgins. Plenty of asexuals lead “normal” lives, and have relationships, happy marriages and even children. Anne Hooper, an author and sex and marital therapist, describes one such asexual woman she encountered: “She was happily married and was a wonderful mother to her children, but she simply did not have any sexual desire. Even vibrators and sex therapy had no effect.”

So what makes someone asexual? The researcher who first noticed the existence of this group of people is Professor Anthony F Bogaert, who specialises in research into sexual behaviour. He discovered factors that make asexuality more likely. He found that the biggest single factor was gender — women are more than twice as likely to be asexual as men. Poor health was another. Asexual women also started puberty later and were more likely to be religious than sexual women.

If you’re confused, don’t worry. Even Bogaert could only conclude: “The results suggest that a number of pathways, both biological and psychosocial, contribute to the development of asexuality.”

Of course, some asexuals do have a physical or mental illness. There is evidence that schizophrenia and depression can wipe out desire, and sex phobias can also affect libido. One contributor to the website says just hearing people talk about sex makes her physically sick.

Sexual-aversion disorder (an intense dislike of sex) is another problem, which can affect people who suffer from panic attacks. Louise Fenton is one of them. “I was asked by a healthcare professional earlier in the year if I had had any sexual experiences or relationships,” she says. “When I answered ‘No’, he looked at me in disbelief and said, ‘What, not even kissing?’ I replied I couldn’t see the attraction of having someone else’s slobber all over my face.”

Several members of Aven describe themselves as having Asperger’s syndrome, a mild form of autism. Asperger’s can be associated with sensory problems that make being touched seem intrusive or intolerable.

There are various physical causes of asexuality, including illnesses such as multiple sclerosis. According to Hooper, naturally low testosterone levels can also be a cause, particularly in men.

In women, however, the picture is more complicated. Hooper says that, even among those with a normal hormone profile, between 8% and 12% find it very difficult, if not impossible, to feel aroused. “Even if they do feel slightly sexual,” she says, “they can’t reach orgasm, so they aren’t very motivated to seek out a sexual relationship. For some of these women, testosterone therapy seems to increase desire, arousal and orgasm, but in others, it has no effect.”

Hooper points to research by the Kinsey Institute in America, which suggests that there are specific brain centres that control sex drive: an exciter centre, which permits arousal, and an inhibitor, which keeps it under control. “It may be that for some women, there is more than one inhibitor, or that it may be overactive,” she says.

So what can these women do? “There are drugs that seem to work on suppressing the inhibitor centres, allowing the brain to process sexual sensation,” says Hooper. However, few women are ever diagnosed with an overactive inhibitor, let alone given treatment. And as Fiona Henley, a 40-year-old married mother of three, admits, asexuals don’t necessarily want treatment anyway.

“I could quite happily live the rest of my life without sex,” she says. “I think there have been millions of marriages like mine through history, but it’s only recently that women have been expected to be wives, mothers, have a great job and be sex goddesses, too.” For now, Henley feels her lack of sex drive is something to keep quiet about.

But that could all be changing. What is different about the new breed of asexuals is that they are proud to say they are indifferent to sex. And by defining asexuality not as a disorder but simply another form of sexuality — alongside heterosexuality and homosexuality — they are stating they are positively glad to be A.