More than one in eight adults in the US show signs of being addicted to the internet, a study has shown.
"Addicts" showed signs of compulsive internet use, habitually checking e-mail, websites and chat rooms.
More than 8% of the 2,513 respondents to the Stanford University phone survey said they hid their use from partners.
A typical addict is a single, white college-educated male in his 30s, who spends more than 30 hours a week on "non-essential" computer use, it found.
"We often focus on how wonderful the internet is; how simple and efficient it can make things," said Dr Elias Aboujaoude of the Stanford University School of Medicine and one of the researchers behind the study.
"But we need to consider the fact that it creates real problems for a subset of people."