The number of 11 to 17-year-olds showing signs of problem gambling has more than doubled, according to a survey by the UK's gambling watchdog.
Nearly one in 10 young people surveyed said gambling had resulted in them telling lies, while around one in 12 said it had led to arguments.
The Gambling Commission quizzed 3,869 young people in England, Scotland and Wales. Of those, 1.5% were to deemed to have a problem, a big rise on the 0.7% reported in the 2023 survey.
The most common types of gambling young people spent money on were arcade gaming machines and placing a bet or playing cards with friends and family for money, the report said.
These types of gambling are all legal.
Those reporting that gambling made them feel happy rose from 17% last year to 26%.
The majority of young people surveyed - 82% - said they felt well informed about the risks of gambling.
But more than one in 15 young people reported being worried about gambling by family members.
And more than 60% of young people surveyed said they had seen or heard gambling advertising, a significant increase on last year.
According to the Gambling Commission, the signs of problem gambling in young people include using it to escape from feeling bad and spending increasing amounts to get the same excitement.
It can also include taking money without permission to gamble, feeling bad when trying to cut down on gambling, and returning the next day to try and win back money lost.
Former Conservative cabinet minister Sir Iain Duncan Smith told the BBC the government should bring forward tougher gambling regulations more quickly.
Sir Iain, who campaigns on gambling harms, said that gambling companies "use ruthlessly apps and everything else to get to younger people".
He added: "They're rapacious, and the damage that's being caused is quite astonishing really."
The previous Conservative government set out proposals for tighter regulation of gambling firms in 2023, which Sir Iain called "good but not good enough”, arguing they “backed off” over advertising.
A government spokesperson said Labour recognised "the impact harmful gambling can have on individuals and their families and we are absolutely committed to strengthening protections for those at risk, including young people".
"Ministers are currently considering the best available evidence, including the Gambling Commission's recent statistics, and the full range of gambling policy and will update in due course."
From August, the Gambling Commission brought in new protections to help prevent young people from accessing gambling illegally.
All licenced gambling providers have to verify the age of anyone who looks to be under 25.
Tim Miller, who leads on research for the Gambling Commission, said that while they are able to strengthen protections on regulated forms of gambling, "young people often gamble in ways that do not require regulation, such as betting with their friends.
"Yet these forms of gambling can also lead to some experiencing harm."
Just over one in 20 of those surveyed who had spent their own money on gambling said it had made it hard to put effort into their schoolwork at least some of the time.