People who send large numbers of text messages and emails may have a mental disorder, a doctor writing in a leading psychiatric journal said.

Jerald Block, writing in the latest issue of the American Journal Of Psychiatry, said "internet addiction" was a "common disorder" that deserved inclusion in a manual of mental disorders used by health professionals.

Those with the condition suffered withdrawal symptoms of anger and tension when a computer was inaccessible, and often lost their sense of time through excessive use, Dr Block said.