Researchers investigating links between gambling and family violence say they are shocked by the evidence they have gathered.
A Melbourne University study has found nearly half the family members of a problem gambler had experienced violence in the previous 12 months.
Some relatives have also reported becoming so frustrated by the gambling problems they would take it out on children.
Professor Alun Jackson says the study is the first in the world to examine this hidden problem and reveal the strong link between problem gambling and violence within families.
"It's not just about partners, it's now involving broader families, so it's bringing in parents, it's bringing in parents-in-law, it's bringing in siblings," Professor Jackson said.
The study questioned 120 people who sought help for a family member with a gambling problem.
It has found nearly half reported violence within their family in the previous 12 months.
Professor Jackson says the frustrations of a gambling relative drove one in five people to violence themselves, sometimes against the gambler and other times against children.
"What it's really showing is that the impacts of the problematic gambling are not just on couples or the nuclear family but on the broader family network as well.
"And a lot of those people are, I guess as an act of desperation, turning to some level of violence to try and change the situation.
"They are often the victims of violence by extended family members, particularly parents, parents-in-law, who are often stepping in to try and protect their family member.
"For example a problem gambling mother will be abused by her partner who is at the end of their tether and then she will displace that violence onto children.
"So we know children of problem gambling families are subjected to much higher rates of child abuse than the general community."
Professor Jackson says during the study the researchers doing interviews were often shocked at the harm inflicted.
"People have in mind that it's really only violence if it is physical. What came home to us very strongly is how debilitating it is to live under threat of violence day in and day out," he said.
Professor Jackson said when families with problems attend Australia's gambling help services they are not being asked the right questions and the services are failing to stop relatives hurting each other.
"Nobody knew the extent of family violence in these problem gambling families until we asked and typically it's not screened for," he said.
"We've suggested that problem gambling services must screen for the presence of violence because there's no point trying to work on an individual's problematic gambling without taking the whole family context into account."
The study has been published in the Asian Journal of Gambling and Public Health and is part of a broader project in Australia, New Zealand and Hong Kong.
It will continue until June next year.