The Priory clinic reports a rise in lifestyle addictions: shopping, sex, the internet - even texting. But do these habits really wreck lives in the way that drugs or alcohol can?

"Are you a text addict?" asks an advertisement for the mobile-phone company Orange. "Just think what you could do with 1,825 text messages..." It is only marketing spiel, of course, but this month the Priory Group announced that it was treating genuine text-message addicts. And that these people were hooked on their mobile phones as others might be hooked on gambling or sex.

"Mobile phones, like internet chat rooms, are addictive because they give people a reward - the reward is a reply," says Dr Austin Tate, the medical director of the Priory Hospital Marchwood, in Hampshire. "You can feel isolated or insignificant, and you can send someone a message and get one back. That response gives you the hit that you want and makes you want to do it even more."

The Priory Group, a private mental healthcare provider with many famous clients, also reports a rise in all behavioural addictions, which include gambling, sex, shopping, exercise and the internet, as well as mobile-phone texting.

A behavioural addiction is one that does not involve the ingestion of a psychoactive substance such as alcohol or a drug. Over the past decade, self-help groups for people suffering from these non-drug addictions have sprung up. In Britain, you can now attend "anonymous"-style groups for sex addicts, sex and love addicts, gamblers, workaholics and debtors.

As ever, the famous have led the way. In 2001, the tennis player Serena Williams confessed to a compulsive online shopping habit. Michael Douglas is reportedly a reformed sex addict. Halle Berry's husband, Eric Benet, is reported to have received treatment for sex addiction.

Despite the increasing numbers of people seeking help, these conditions remain controversial, especially the new breed of technology-related addictions. "Saying that you are addicted to texting is like saying you are addicted to picking your nose. It's just a stupid habit," says Dr Robert Lefever, the director of the PROMIS Recovery Unit, a private addiction-clinic. "Thousands of people die in this country every year because of alcoholism. Texting is not killing people. It's not destroying families. This is trivialising addiction."

The question is whether a dependency on sex, shopping or texting should be classed as an addiction, or whether it is, in Lefever's words, just a "stupid habit". Professor Mark Griffiths, a professor of gambling studies at Nottingham Trent University, has researched behavioural addictions for 16 years. He strongly believes that they are just as serious as more conventional addictions. "In terms of the effect that it has on an individual, a gambling addiction is just as devastating as alcohol or heroin. People do commit suicide and have health problems as a result of their behavioural addictions," he says.

Griffiths argues that all addicts follow the same pattern of behaviour, no matter whether they are hooked on chat rooms or cocaine. "If someone is addicted to a particular activity, it is the single most important thing in their life. They do it to the neglect of everything else, build up tolerance to it over time, use it as a reliable and consistent way of modifying their mood, and get withdrawal symptoms. If all these criteria are fulfilled, they are an addict."

This outline tallies with the experience of David, a middle-aged company director, who was addicted to shopping for more than a decade. Spending hundreds of pounds on furniture and clothes in a single buying spree, he built up debts of more than £20,000, which he could not repay. "It was out of all proportion to everything else in my life," he says. "I think I spent because I was depressed and disappointed with life. I wanted to change the way I felt about myself. When I didn't spend, I felt deprived and unhappy."

Eight years ago, he went to his first meeting at Debtors Anonymous and slowly brought his spending under control. "It was a very slow process, but I learnt not to use my credit cards, to record everything I spent and to look for a quality of life," he says. "Debtors Anonymous is my Alcoholics Anonymous." His self-help group, like many others in Britain, follows the 12-step recovery programme developed by AA.

You might think it won't be long before Text-messagers Anonymous is formed. However, this problem may not be as widespread as the reports from the Priory Group suggest. Mark Griffiths believes that there are very few genuine texting addicts. "You'll probably find that the number of text-message addicts who reach the same scale of devastation and destruction in their lives as alcoholics or drug addicts is very small."

Deirdre Boyd, the editor of Addiction Today, says that no one has called the magazine's helpline complaining of text-message addiction. "I do believe that text-message addiction is possible - it has all the necessary components, in that it would cut you off from your emotions and other people," she says. "But I've yet to come across an addict."

Even the Priory Group, which reported the phenomenon, admits that the problem is small. Austin Tate said he could not discuss the condition because he had not seen enough cases "to get a true feel for it". Steve Stephens, the Priory Group's national addiction services director, said he had no statistics on the condition, but he does believe "that we are beginning to get a rise in people who are problematically using texting and the internet."

Addiction to the internet was first reported in the mid-1990s. In the United States, the Center for Online Addiction was opened in 1995. The organisation claims that there are 11 million internet addicts in the US. "People do become addicted to the medium of the internet, particularly those who frequent chat rooms or who play online fantasy role-playing games," says Griffiths. "The internet is a non-threatening environment where people can become things that they are not. They can change their personas and make themselves feel better about themselves."

However, unlike the Center for Online Addiction, he believes that the number of true internet addicts is "infinitesimal in comparison to the number of people who are addicted to gambling". In the past eight years, he has encountered only six people he would class as internet addicts. Austin Tate has come across "more than 10".

It is all a question of the criteria used to diagnose addiction. "According to some of the studies that have been done into internet addiction, anyone who uses the internet for more than four hours per day is an addict," says Griffiths. His own criteria are far stricter. An activity has to be the single most important thing in a person's life. A true addict uses that activity to reliably change their mood, builds up their use over time, and suffers both physiological and psychological withdrawal symptoms.

Not all the people now attending self-help groups for a behavioural addiction would fit these criteria. Certainly, only a small minority of those who are labelled addicts by the media would fit.

Is the real reason for the reported rise in behavioural addictions simply a blurring of the definition of addiction itself? People are now more keen to describe themselves as addicts. "The culture now is that we want to be blameless. Attaching a label, such as addiction, enables people to say, 'It's not my fault,'" Griffiths says. "The reason why Michael Douglas comes out and says, 'Yes, I'm a sex addict,' is because this is a way of attributing blame elsewhere for his sexual indiscretions."

More addicts in the population also means more business for the clinics who treat them. The Priory Group now offers a free addiction assessment with a therapist for anyone seeking help for an addiction, to discuss the extent of their problem.

In the absence of detailed and focused research, the experts are left to disagree over whether behavioural addictions really are on the increase, and - if they are - for what reason. Austin Tate at the Priory believes these addictions are on the rise. "It's because of increased accessibility," he says. "The internet and mobile phones have only become widely available in the past few years. And if you look at gambling, if anyone wanted a flutter when I was a boy, they had to give their bet to a bookie's runner who was usually a dubious-looking fellow who hung around the pub and took the slips to the bookie. Now you can bet on anything."

Griffiths agrees that addiction to gambling is increasing as a result of the deregulation of the industry. However, he's not convinced that all behavioural addictions are rising in the same way. "There are other behaviours, such as eating and having sex, that we've always done. And my guess is that the prevalence rates for addiction to these behaviours have always been the same. The difference is that people are now labelling it and getting help."

Meanwhile, the Orange mobile network won't be drawn either way on the issue. "There is nothing in our research that indicates whether text-message addiction exists or not," says a spokesperson. "We see no evidence for it."