Some teenagers are racking up debts of $30,000 through online sports betting, and the number of young people asking for help has doubled in three years, the University of Sydney's Gambling Treatment Clinic says.

The treatment centre's operator says the bulk of their clients used to be poker machine addicts, but now they are treating mostly young men in trouble with online betting.

State of Origin is one of the most popular sporting events in Australia and Wednesday night's game was watched by millions of people.

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Just before kick-off viewers were given the latest odds and the following Sportsbet advertisement was played during the game:

"With Sportsbet for Origin Game 1, place a head-to-head bet and if your team lose by eight points or less — cash back up to $100."

It is this sort of marketing of online betting that is being blamed for an increase in the number of young people developing gambling addictions.

Dr Christopher Hunt has been a clinical psychologist at the University of Sydney's Gambling Treatment Clinic for eight years.

"When I first started, we pretty much never saw anyone of that 18 to 25-year-old demographic, but what we've seen is a dramatic increase, especially over the past three, four years," he said.

"So in the past three years we've seen a doubling in the number of people from that demographic ... in 2012 we had 23, and last year we had 50, and this year we're on track to see even more.

"It seems to be young men who are getting themselves into trouble, and I guess that's particularly related to the fact that it's tied to sports and horse betting, because those sorts of gambling are almost always men's preferred forms of gambling."

Dr Hunt remembered one young man in particular, who took money from his employer to pay off gambling debts and lost his marriage and employment prospects in a health profession as a result.

"It got to the point that just before he came to see us he was thinking about killing himself and that was essentially the trigger that brought him into our clinic," he said.

Using sports knowledge to make money 'ultimately a false belief'

Dr Hunt said he believed the increased promotion of online gambling is to blame for the rise, as well as the easy access to online betting through smartphones and tablets.

He said while sporting codes had introduced some measures to not talk about odds during a game, sports betting was still promoted during advertisement breaks.

"This escalation of this marketing of sports betting seems to have occurred just before we're seeing this rise in gambling in young men," he said.

"So while we haven't done the studies to conclusively say that these things are caused by this increase in marketing, it definitely seems to have occurred at the same time.

"When you're constantly pushing this message that betting is glamorous, betting is fun, betting is a way you can be a winner [and] you can turn your interest and knowledge of sports into money, it's an incorrect statement essentially, but it's part of the core that's really getting people trapped into these gambling problems.

"It's this belief that if I have an interest in sports, if I know something about sports, I can use that to make money, which at the end of the day is ultimately a false belief."

Dr Hunt said community attitudes towards gambling must change and urged young people who have started getting into trouble to get help early.

"Really nip it in the bud now because the people that we do see in their 30s and their 40s and their 50s, they first started getting into problems with gambling in their early 20s," he said.

"Whilst at that stage it might not have been as problematic for them, that's when it started for pretty much all our clients and by the time we're seeing people in their 40s and 50s, what we're seeing is people that have lost houses, people who have lost jobs, people who have lost marriages, people who have lost custody of their kids as a result of their gambling."

Support is available through the Gambler's Help website gamblershelp.com.au or by calling the free Gambling Help Line on 1800 858 858.