Adolescents who suffer from mental illness and don't feel connected to their schools, communities and families are more likely to engage in delinquent behaviour, a new study says.

The study, "Improving the Health of Canadians: Mental Health, Delinquency and Criminal Activity,"was released Tuesday and conducted by the Canadian Institute for Health Information.

It found that 12- and 13-year-olds who are hyperactive and depressed are more likely to engage in behaviour like property vandalism or destruction. In contrast, youth aged 12 to 15 who have good stress-management skills and high self-esteem are more likely to never engage in aggressive behaviour.

The findings also showed that 21 per cent of youth who said their parents often yelled at them or threatened to hit them claimed that they often engaged in aggressive behaviour. Overall, only 10 per cent of youth overall claimed to act aggressively.

The study's authors said that their findings support other research that suggests childhood delinquency is more common among youth whose parents don't offer them positive support systems.

About 65 per cent of youth who reported being involved in school activities and 66 per cent who said they like school said they've never engaged in aggressive behaviour. However, 47 per cent of kids who did not engage in school and 47 per cent who did not like school reported that they often act aggressively.

The study suggests that mental illness and difficulty fitting in socially are risk factors that can make youths more likely to engage in destructive behaviours when they are young and as they grow into adulthood.

Patricia Campbell, a program manager with Banyan Community Services, an outreach program for at-risk youth in Kitchener, Ont., appeared on CTV's Canada AM on Tuesday. She said that the study is the first to outline how keeping kids out of the criminal justice system should be a collaborative community effort.

"I was really impressed how the report highlights the key risk and protective factors for kids on the trajectory to enter the youth justice system and our need for early intervention and crime prevention to mitigate those risk factors to keep our kids out of our youth justice system."

The study found that 10 per cent of the more than 30,000 patients who were admitted to hospital for mental illness in Ontario from 2006 to 2007 had either been charged or involved with a crime. Almost 30 per cent of these patients had some history of criminal behaviour that involved the police.

Phil Upshall, president of the Mood Disorders Society of Canada, told Canada AM that the study should finally make clear to government health agencies, schools, community groups and families that sending at-risk kids to jail will only cause them greater problems in the future.

"Give us the opportunity to remove, hopefully, a significant number of kids from the criminal system and put them in the health system where they belong," Upshall said.

"Once you're into the criminal system and are processed by it, you've got (criminal) records."

Annie Smith, executive director of the McCreary Centre Society in Vancouver, which conducts research and runs programs related to youth health issues, told Canada AM that kids need to develop a sense of self-worth in order to stay out of trouble.

"Instead of targeting one specific behaviour, we need to look at building strength and capacity in young people," Smith said.

"So activities that raise their engagement in community activities, raise their self-esteem, allow them the opportunity to develop skills and also to have optimism for the future."