In the first large-scale study of its kind, University of Leeds psychologists found evidence that users can develop a compulsive internet habit, replacing real-life social interaction with online chat rooms and social networking sites.
This type of addictive use can have a serious impact on mental health, according to their research.
"The Internet now plays a huge part in modern life, but its benefits are accompanied by a darker side," said lead author and Leeds lecturer Catriona Morrison in a statement. "While many of us use the internet to pay bills, shop and send emails, there is a small subset of the population who find it hard to control how much time they spend online, to the point where it interferes with their daily activities."
The researchers evaluated Internet use and depression levels of 1,319 people aged 16 to 51. They found that 1.2 percent of the group was considered "Internet addicted."
While that number is small, it's actually twice the rate of addiction to gambling in the U.K., at 0.6 percent.
Compulsive Internet users had a higher incidence of moderate to severe depression than non-addicted users, and they spent proportionately more time browsing online communities, gaming sites and sexually gratifying websites, according to the study.
The chicken-or-egg question: Do depressed people use the Internet more heavily, or does heavy Internet use lead to depression? It's unclear.
What is clear, however, is that for a small subset of people, there could be a link between the two.
In other words, excessive Internet use has become a mental health condition.
In the study, young people were more likely to be internet addicted than middle-aged users. The average age of the addicted group was 21 years old.
The Leeds study is the first large-scale study of Western young people to consider the relationship between internet addiction and depression.
Findings will be published in next week's edition of the journal Psychopathology.