Psychologists in the UK have said there is a strong link between the time individuals spend surfing the internet and a person's mental health.
Scientists from Leeds University said that people who spend a lot of time on the internet are more likely to suffer from depression and feelings of unhappiness.
The study, which was published in the journal Psychopathology, found that 1.2 per cent of people surveyed were "internet addicts".
Many in this category were deemed to be depressed, although scientists pointed out they were unsure whether the internet was the cause of the depression.
Study leader Dr Catriona Morrison, from the Institute of Psychological Sciences at the University of Leeds, said: "The internet now plays a huge part in modern life, but its benefits are accompanied by a darker side."
"There was a high correspondence between the amount of time spent on the internet and levels of depression. If you look at how dependent people feel they are on the internet that is likely to correspond with how happy or sad they feel," she added.
The researchers said young people were significantly more likely to show addictive symptoms than older people.See all the latest jobs in Medical Devices