Researchers found that spending excessive periods of time surfing the internet left people in 'negative moods' and, like drug addicts, when heavy internet users go back on the web their negative moods lift, the Daily Mail reported.
Our results show that around half of the young people we studied spend so much time on the net that it has negative consequences for the rest of their lives, said Professor Phil Reed, from the university's psychology department.
The study, published in the international journal Plus One, was carried out on 60 volunteers with an average age of 25 at Swansea University's College of Human and Health Sciences.
The researchers first gave volunteers a series of psychological tests to find out their level of addiction to the internet, their mood, their anxiety level and whether they were depressed.
They were told to browse the internet for 15 minutes, then they were tested again for mood and levels of anxiety.
Using the internet had a 'striking' impact on the positive mood of those who were addicted to the web, and their comedown was far more pronounced than those who used it less often, the research noted.
And these withdrawal symptoms may promote a vicious cycle.
"The immediate negative impact of exposure to the internet on the mood of internet addicts may contribute to increased usage by those individuals attempting to reduce their low mood by re-engaging rapidly in internet use," the study said.
The negative impact of excessive internet use can be seen across a wide range of aspects of the addict's life. Internet addiction was associated with long-standing depression, impulsive non-conformity, and autism traits, it concluded.