Two fifths of young people aged 11 to 16 gambled in the past year, according to a report.
Fruit machines at an arcade, pub or club were the most popular form of gambling, followed by playing cards for money with friends and buying scratch cards, the largest study of its kind, by Cardiff University academics, found.
Placing a private bet among friends and buying lotto tickets were also among the top gambling activities.
Of the 41% who said they had gambled in the past 12 months, 16% said they felt bad as a result.
Boys were more frequent gamblers than girls, while young people from minority ethnic groups and students who felt that they did not belong in their school were also more likely to engage in gambling and to feel bad about the experience.
Dr Graham Moore, from the Centre for the Development and Evaluation of Complex Interventions for Public Health Improvement, where the research was conducted, said: “While over the past 20 years or so, lots of adolescent risk behaviours like smoking and drinking alcohol have become less common, we are seeing the emergence of new risk behaviours in today’s society. Our research suggests that gambling might be emerging as a new public health issue.
“The evidence shows that people who gamble earlier in life are more likely to become problem gamblers in adulthood. The fact that there is widespread opportunity to gamble and limited education regarding its risks means that adolescents are particularly vulnerable to its harms. More work needs to be done, with policymakers, schools, families and young people, to understand how young people’s exposure to gambling can be reduced.”
Researchers gathered data from more than 37,000 students who completed gambling questions as part of the 2017 School Health Research Network Student Health and Wellbeing Survey, which represents 193 secondary schools in Wales.
Respondents were asked a range of questions about gambling, including if they had gambled in the past 12 months, how often they had felt bad about gambling and what sorts of gambling they had participated in.
In the UK, commercial gambling is legal for those aged 18 and over with two exceptions. Young people between 16 and 18 can legally buy National Lottery products, including draw-based games, scratch-cards and online instant wins, and there are no age restrictions on category D games machines, which include fruit machines.
Lead author Professor G.J. Melendez-Torres, who conducted the research at Cardiff University, said: “Problem gambling is associated with lower self-esteem, poorer school performance and an increased risk for other addictions, as well as feelings of guilt, shame and self-hatred.
“Our findings demonstrate the importance of educating young people and parents about the potential harms of gambling and support policy recommendations for schools and the education sector to raise awareness of these issues.”