British psychologists have found evidence of a link between excessive internet use and depression, research published today has shown.

Leeds University researchers, writing in the Psychopathology journal (abstract here – subscription required for full pdf), said a small proportion of internet users were classed as internet addicts and that people in this group were more likely to be depressed than non-addicted users.

The article on the relationship between excessive internet use and depression, a questionnaire-based study of 1,319 young people and adults, used data compiled from respondents to links placed on UK-based social networking sites.

The respondents answered questions about how much time they spent on the internet and what they used it for; they

also completed the Beck Depression Inventory – a series of questions designed to measure the severity of depression.

The report, by the university's Institute of Psychological Sciences, said 18 of the people who completed the questionnaire – 1.4% of the total – were internet addicts.

"Our research indicates that excessive internet use is associated with depression, but what we don't know is which comes first – are depressed people drawn to the internet or does the internet cause depression?" the article's lead author, Dr Catriona Morrison, said.

"What is clear is that, for a small subset of people, excessive use of the internet could be a warning signal for depressive tendencies."

The age range of all respondents was between 16 and 51 years, with a mean age of 21.24. The mean age of the 18 internet addicts, 13 of whom were male and five female, was 18.3 years.

By comparing the scale of depression within this group to that within a group of 18 non-addicted internet users – again of a mean age of 18.3 years and made up of 13 males and five females – researchers found the internet addicts had a higher incidence of moderate to severe depression than non-addicts.

They also discovered that addicts spent proportionately more time browsing sexually gratifying websites, online gaming sites and online communities.

"This study reinforces the public speculation that over-engaging in websites that serve to replace normal social function might be linked to psychological disorders like depression and addiction," Morrison said.

"We now need to consider the wider societal implications of this relationship and establish clearly the effects of excessive internet use on mental health."

The six-page report is the first larger-scale study of young western people to consider the relationship between internet addiction and depression.

Much of the previous research into the subject has been carried out in east Asia.