Sex addiction has been made “fashionable” by celebrities such as Russell Brand, who claims in his autobiography, My Booky Wook, that his relentless desire for “how's yer father” is a compulsion beyond his control. Well, I've spent the past year living with sex addiction - not my own, you understand, but while researching a book on John F. Kennedy - and the more I study it, the more sceptical I have become that sex addiction is a geniune condition.

My starting point was a 1961 nuclear arms summit in Bermuda. The British Prime Minister of the time, Harold Macmillan, was embarrassed when he encountered President Kennedy's White House intern crouching in the back of a limousine, waiting to service the Leader of the Free World. Kennedy famously made the excuse: “If I don't have a woman for three days, I get terrible headaches.” Here was the archetypal philanderer claiming to experience withdrawal symptoms, a cardinal sign of addiction.

President Kennedy was the most powerful man in the world. He was young, handsome and witty, and there was no shortage of women who fell for his charms. He shamelessly propositioned aides, socialites and starlets, disdained foreplay and, according to the Hollywood actress Angie Dickinson, climaxed within about 20 seconds.

JFK suffered numerous chronic ailments throughout his life. White House physicians treated him for Addison's disease, thyroid insufficiency, inflammatory bowel disease, peptic ulcers, prostatitis, asthma, osteoporosis and a collapsed vertebra. That he could get out of bed in the morning is staggering, let alone bed thousands of women. But these health problems also explain the President's headaches, as does the stress of being the President. JFK didn't report withdrawal symptoms from sexual activity; he claimed a dependence on seducing a woman every three days. Any dependence that he had on sex must have been purely psychological.

Russell Brand, Michael Douglas and, most recently, the actor David Duchovny (who checked into rehab in Arizona in 2008) have all claimed to have “sex addiction”. Do these rich and famous men really have an illness that renders them incapable of resisting temptation? Or are they just looking to shift the blame for behaviour that's more a result of abundant sexual opportunity?

Dr Philip Hopley, an addiction specialist at the Priory Hospital at Roehampton, southwest London, and a consultant psychiatrist for LPP Consulting, says that public scepticism is “understandable”. He says: “The major concern is where sex-related problem behaviour is labelled an ‘addiction' when in fact poor decision-making and/or impulse control lie at the root of the problem. What constitutes normal, average or healthy sex? There is no recommended limit for adults as there is for, say, alcohol - and if there was, would it be different for males and females?”

Phillip Hodson, a Fellow of the British Association of Counselling and Psychotherapy, points out that the whole idea of having an addiction to a natural drive is problematic. “The excuse, of course, is that nature wants us to have sex to make babies and isn't bothered about rationing the drive. It's the same with eating. You cannot really be ‘addicted' to normal drives. What's the cure - to stop procreating or eating?” Yet perhaps one can't really blame people for using the term “addiction”, because compulsivity or mania don't have quite the same ring. “Sex maniac” sounds like something out of a Carry On film.

Dr Hopley says that patients who seek help often claim to be suffering from sex addiction and be troubled by sex-obsessed thinking, compulsive sexual behaviour and/or hypersexuality, “However these problems often stem from mood disorders, obsessive compulsive disorder, personality disorders or mental impairment. Not infrequently, alcohol and drug misuse are relevant coexisiting conditions, exerting a significant disinhibiting effect.”

Consider the case of Valerie, a patient being treated for sex addiction. “Any time I met a guy who didn't respond to me sexually, it would make me determined to have him,” she says. “The lowest point came when I tried to seduce my best friend's fiancé.” She may have been given a diagnosis of sex addiction, but her history reads like someone with a histrionic personality disorder - which is characterised by a pattern of attention-seeking, including an excessive need for approval and inappropriate seductive behaviour.

Russell Brand and David Duchovny appear betteradjusted but, because of their celebrity status, when they walk into a room, they know it's possible that there will be women willing to have sex with them. Brand relates how he would seduce adoring groupies after his comedy gigs. This doesn't sound pathological at all. It sounds like someone choosing immediate gratification. How many young men given these opportunities would become “sex addicts”? I don't think it's appropriate to demonise unattached people for enjoying the perks of good looks, fame and success.

It's only once they have married or are in a committed relationship that the situation changes. In the aftermath of being caught, that person has to face the consequences of his or her conduct - broken relationships, professional embarrassment or social stigma. Then its convenient for a bad choice to be repackaged as a disease and it's in that person's interests for the outside world sees their behaviour that way.

Dr Andrew Collins, a psychiatrist with an interest in the media and the history of psychiatry, points out that addiction has lost its “strict medical meaning because people label themselves addicts for cultural or social reasons”. He says: “In the pastpsychiatrists attempted to differentiate between irresistible and unresisted impulses. Irresistible impulses have historically been accepted as mental illness. But unresisted impulses that led to misconduct were ascribed to depravity.”

Jackie Kennedy suspected that her husband was womanising but never caught him in the act, so she turned a blind eye rather than suffer the ignominy of divorce. Nowadays fewer women put up with it. The likes of Duchovny and Brand are just reaching for a convenient excuse when they claim that their urges are irresistible - irresistible isn't the same as hard to resist.

I have more respect for Hugh Grant. Following his arrest for “lewd conduct” with the prostitute Divine Brown in 1995, Grant appeared on the Tonight Show in the US and accepted responsibility: “I think you know in life what's a good thing to do and what's a bad thing, and I did a bad thing.”

Doctor Hopley agrees that some people cling to a medical label to abrigate responsibility for their behaviour. “But using such terminology can at least dispel the taboo around disclosing problem sexual behaviour, enabling people to seek help - and hopefullyto limit the damage they are causing to themselves and others.”

Of course, our attitudes to sexual misconduct also depend on the morality of the times. Many psychiatrists once branded homosexuality a disease; now we see how convenient this was for a less enlightened time. Dr Collins suggests: “Social utility is behind the currency of terms such as ‘sex addiction', because questions of individual responsibility and morality aren't just difficult for society to deal with; they're difficult for health professionals too.”

In John F. Kennedy's day, there was no such term as sex addiction; men were called philanderers, and women much worse. Today promiscuity is sometimes labelled an addiction, by those who practise it, those who treat it and those who write about it. Calling it a disease merely excuses us from having to take a moral view on issues such as monogamy, how many partners are too many, and how much sex is too much.

American Adulterer by Jed Mercurio is published by Jonathan Cape (£12.99)

Times recommends

• McDonald’s: the world’s local restaurant
• Help me to be a mum: a foyer to fulfilment
• A life online: God likes a laugh