A growing number of young people are becoming addicted to online video games, a leading addiction specialist has warned.
While computer games have now been around for decades, the move into online games combined with the relentless spread of smartphones and tablets to play them on, pose particular addictive risks, said Dr Colin O'Gara, a psychiatrist at St John of God's Hospital.
Parents should restrict children's access to these games because a proportion of users will develop problems with them, he added.
The biggest problem is with roleplaying games and especially those where the player can accumulate currency, he said.
Online gaming allows players to interact with thousands of other users worldwide in Massively Multiplayer Online games (MMOs).
While gaming is not currently classified as an addiction by the American Psychiatric Association, a condition called Internet Gaming Disorder has been identified as a condition that requires further study.
Dr O'Gara said there were no figures available to quantify the scale of the problem in Ireland, but a growing number of people in their late teens and 20s were being referred with gaming addiction issues, sometimes in combination with other addictions, such as cannabis use.
"I have seen cases of serious functional decline where people's behaviour is being criticised and it is interfering with their lives and getting in the way of other activities, similar to what happens with other addictions," he said.
This problem was virtually unheard of 10 years ago, but the surge in computer and smartphone penetration into homes meant it was no longer rare for GPs to refer on cases of excessive gaming.
It made sense for parents to restrict access to online gaming, said Dr O'Gara.
Where children are already engaged in these activities, adults should learn about them and find ways to manage their access.
"The reality is that the majority of kids won't run into problems with online gaming, but it's impossible to predict which are the ones that will, so it makes sense to be cautious," he said.
Video games have overtaken the movie industry worldwide with sales of €80bn while in Ireland sales rose by 11pc last year to €206m, according to figures compiled by gaming industry expert Jamie McCormick.
"The whole online games segment, including apps and shortform games on mobiles, has really broadened the demographic beyond the traditional console users, so now you have all ages and nearly as many women playing games as men, more in some cases," he said.
Some 30pc of nine-year-old boys and 12pc of girls were found to be playing video games for at last one hour a day in a Growing Up in Ireland (GUI) survey - though that was in 2009 before the huge surge in smartphones and tablet ownership. Another GUI survey of five-year-olds found that 18pc of these who spent more than three hours a day playing video games, on the internet or watching TV had emotional or behavioural difficulties, compared with 10pc of those who had low levels of screen time.
Studies at the University of Iowa have highlighted how the content of video games can influence child behaviour.
Social games that portray caring and cooperative behaviour increase levels of empathy and helpfulness, while repeatedly playing violent games encourages aggressive behaviour.