Any direct causal link between internet use and depression remains unclear
Lead author Dr Catriona Morrison said: "The internet now plays a huge part in modern life, but its benefits are accompanied by a darker side.
"While many of us use the internet to pay bills, shop and send e-mails, 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 internet addicts were significantly more depressed than the non-addicted group, with a depression score five times higher.
The average score of the internet-addicted group put them in the category of moderate-to-severe levels of depression.
There is no good evidence that the problem is the internet itself
Dr Vaughan Bell of King's College London
"Now we need to investigate the nature of that relationship and consider the issue of causation."
Critics of the research say that internet addiction cannot be diagnosed reliably.
Dr Vaughan Bell, from the Institute of Psychiatry at King's College London said that by definition, those identified as "internet addicts" are emotionally distressed, so the conclusions are "not a big surprise".
In terms of cause and effect, he pointed out that previous research has suggested that people who are depressed or anxious may be more likely to use the internet rather than the other way round.
He added: "There are genuinely people who are depressed or anxious who use the internet to the exclusion of the rest of their lives, but there are similar people who watch too much TV, bury themselves in books or go shopping to excess.
"There is no good evidence that the problem is the internet itself."
Mental Health charities said the way people spend their time and the kind of social interaction they engage in could well impact on mental wellbeing.
Source : http://news.bbc.co.uk