Just as a drug addict may face withdrawal symptoms, people who use the internet a lot may experience significant physiological changes such as increased heart rate and blood pressure when they go offline, scientists have found.

"We have known for some time that people who are over-dependent on digital devices report feelings of anxiety when they are stopped from using them, but now we can see that these psychological effects are accompanied by actual physiological changes," said study lead Phil Reed, Professor at Swansea University in Britain.The study involved 144 participants, aged 18 to 33 years, having their heart rate and blood pressure measured before and after a brief internet session. Their anxiety and self-reported internet-addiction were also assessed. 

The results showed increases in physiological arousal on terminating the internet session for those with problematically-high internet usage.There was an average three to four per cent increase in heart rate and blood pressure, and in some cases double that figure, immediately on termination of internet use, compared to before using it, for those with digital-behaviour problems, according to the study published in the journal, PLOS ONE.Although this increase is not enough to be life-threatening, such changes can be associated with feelings of anxiety, and with alterations to the hormonal system that can reduce immune responses. 

The study also suggested that these physiological changes and accompanying increases in anxiety indicate a state like withdrawal seen for many 'sedative' drugs, such as alcohol, cannabis, and heroin, and this state may be responsible for some people's need to re-engage with their digital devices to reduce these unpleasant feelings.However, there were no such changes for participants who reported no internet-usage problems.