The study published in the journal Psychopathology, found that the more time people spent online, the more likely they were to be depressed.
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.
"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."
To determine the relationship between Internet addiction and depression, researchers from the University of Leeds used Internet and social networking sites to recruit study subjects.
After placing online invitations, they got 1,319 responses from online users aged 16 to 51.
The respondents were asked a series of questions via online questionnaires to determine how much time they spent on the web and whether or not they suffered from depression.
Heavy Internet use linked to depression
On analysis, the researchers found that 1.2 percent of the people surveyed were addicted to Internet as well as exhibited symptoms of depression.
The Internet addicts scored five times higher on depression compared to the non-addicts.
"There was a high correspondence between the amount of time spent on the internet and levels of depression," said Dr Morrison. "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."
The researchers noted that these addicts spent more time “on online gaming sites, sexually gratifying websites, browsing, online communities and chat sites.”
It was also found that young people, especially males, had higher tendency to be glued to the web compared to the middle-aged adults.
The study warns that if someone spends most of his time online, replacing social interaction with online chat rooms, this could significantly worsen his mental health.
Such addicts can go for corrective strategies like counseling and cognitive behavioral strategy to get rid of compulsive Internet addiction.
Though the study indicated a strong association between excessive Internet use and depression, it is yet not clear whether Internet addiction triggers depression, or depressed people are drawn towards it, the researchers said.
This possibility will have to be addressed in further research, they said.
"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?" said Dr Morrison.
"Now we need to investigate the nature of that relationship and consider the issue of causation," he added.