Parents take note -- video games are not all bad.

In young children and adolescents they can lead to excessive use and aggressive behavior but a leading expert said that the games ease pain, distract patients undergoing chemotherapy for cancer and help to develop dexterity.

"The degree of attention needed to play such a game can distract the player from the sensation of pain," Professor Mark Griffiths, of Nottingham University in England, said in an editorial in the British Medical Journal.

In patients with arm injuries, the games have been used to increase strength and dexterity while children with learning disabilities have played them to develop spatial ability.

"Therapeutic benefits have also been reported for a variety of adult populations including wheelchair users with spinal cord injuries, people with severe burns and people with muscular dystrophy," according to Griffiths.

Although the reported negative effects, which include wrist pain, hallucinations and repetitive strain injuries, have been widely reported, Griffiths said they tend to be temporary and could be caused by other factors.

"Some of these adverse effects seem to be rare and many resolve when the patients no long play the games," he added.

Griffiths, a professor of gambling studies, called for more studies into the long-term effects of video games and what constitutes excessive use.

"Further research should examine factors within games such as novelty, users' preferences, and relative levels of challenge and should compare video games with other potentially distracting activities," he added.