Mental health professionals in the United States have highlighted the emergence of a new psychiatric problem on a par with alcoholism, drug abuse or obsessive gambling: internet addiction disorder.
It occurs when an American office worker who should be focussing on the tasks at hand is spending hours playing fantasy football on the computer instead. Or when an executive is so attached to his handheld device that he checks it last thing at night and then consults it the moment he opens his eyes in the morning.
Some people spend so much time online that they stop going out, their marriages break up and they are overwhelmed by depression and suicidal feelings.
According to estimates in The New York Times yesterday, as many as 10 per cent of the 189 million internet users in the US could be addicted.
Hilarie Cash, who heads Internet/Computer Addiction Services in Redmond, near Seattle, has identified a specific chemical rush - a dopamine high - which can be generated by even something as simple as receiving an email. She told The New York Times that she has seen instances of anxiety and depression in her patients.
Other internet addiction experts have developed 12-step programmes to wean people off their online habit, or started support groups for the addicts' spouses.
There are many definitions of internet addiction disorder. One by Jennifer Ferris, a psychologist from Virginia, points to seven telltale signs such as a thirst for ever more time spent online, trembling or even involuntary finger movements when the users is away from the computer, dysfunctions in day-to-day relations with friends and co-workers and, at the extreme, the loss of a job or a marriage because of excessive internet use.
However, other professionals argue that internet addiction is merely a new platform for other pathologies such as gambling or obsession with pornography.
Internet use is on the rise. A report by the Pew Internet and American Life Project this year found that more than half of American teenagers were online every day, compared with 42 per cent five years ago.
And its economic impacts are now being quantified. The business consultants Challenger, Gray & Christmas recently estimated that American fantasy football alone was costing US employers $200m in lost productivity every season.Reuse content