Excessive gaming and email/text messaging should be added to psychiatry's official guidebook of mental disorders, according to an article in this month's American Journal of Psychiatry.

Dr Jerald J Block, the article's author, outlined four distinct symptoms displayed by sufferers.

Withdrawal and an associated sense of anger or depression when users cannot reach a computer, the constant need for better equipment and the feeling of social isolation and fatigue are all signs of technology-related mental disorders.

"Attempts to measure the phenomenon are clouded by shame, denial and minimisation," said Dr Block.

The conditions are difficult to treat because internet addiction is " resistant to treatment, entails significant risks and has high relapse rates".

Dr Block said that the problem is most acute in South Korea where internet addiction is one of the country's "most serious public health issues".

"Using data from 2006, the South Korean government estimates that approximately 210,000 South Korean children are afflicted and require treatment, " said Dr Block.

South Korea set up a network of 140 'tough love' rehabilitation centres in November 2006 in a bid to curb the growth of internet addiction among the country's teenaged population.