Schools and family factors play an important role in shaping clusters of health behaviours among teenagers, new research has found.

Researchers at the Economic and Social Research institute examined how four key risk factors for disease - smoking, alcohol consumption, physical activity and diet - cluster together among young adults.

According to the finding, by the time young people reach the age of 17, they generally belong to one of three distinct behaviour clusters:

-A 'healthy' group who do not smoke, drink alcohol rarely, regularly engage in exercise and consume the best quality diet

-An 'unhealthy diet and physical activity' group. These do not smoke, drink alcohol rarely, but have the worst levels of physical activity and the poorest diet quality

-An 'unhealthy smokers and drinkers' group. These have the highest level of alcohol consumption, are daily or occasional smokers, have moderate to low levels of physical activity and poor-to-moderate dietary quality.

Using data from the ongoing Growing Up in Ireland study, the ESRI researchers found that 43% of 17-year-olds fitted into the 'healthy' group category, while 36% fitted into the 'unhealthy diet and physical activity' group.

The remaining 21% belonged to the 'unhealthy smokers and drinkers' group.

The research found that a number of individual and family factors were linked with membership to these groups. For example, young people from working class backgrounds were more likely to be a smoker/drinker, as were young people whose own parents smoked.

Overall, young women were more likely to fall into the two unhealthy groups.

When it came to schools, the researchers found that school policies had little impact on the membership of the various cluster groups. However the socioeconomic composition of students, as well as the school climate, were found to have an important influence.

A major feature was found to be the interaction between the student and their school. Students who had negative interactions with teachers and who were unhappy in school, displayed greater levels of smoking and drinking in particular.

According to one of the research authors, Anne Nolan of the ESRI, the findings show that health behaviours are "interconnected".

"They suggest that a multi-faceted approach is needed to promote positive health behaviours. The increasing emphasis on wellbeing as an area of learning at second level offers further opportunities for promoting positive health behaviours during adolescence.

"The research findings show that measures to promote both school engagement and a more positive school climate, while important for educational outcomes, are likely to have positive spill-overs for other aspects of young people's lives, including health behaviours," she commented.

The research was funded by HSE Health and Wellbeing. According to Helen Deely, interim programme lead for HSE Health and Wellbeing, it is already known that patterns of health behaviour that can lead to chronic illness can be formed at a young age.

"This research is telling us that a positive school environment makes it more likely that young people will experience a sense of belonging and connection, and less likely that young people will turn to risky health behaviours, such as using tobacco and alcohol, to cope with their feelings of isolation and disconnection," she said.

However, while the HSE will continue to work in partnership with the Department of Education in relation to teacher training and resource development to support wellbeing promotion in the school setting, Ms Deely pointed out that schools "are not the only influences on adolescent health".

"The intergenerational transmission of smoking and drinking alcohol identified in this study reinforces the importance of supporting parents with managing their own health behaviours.

"Preventing unhealthy behaviours taking hold in adolescence is more cost-effective to the State and life-enhancing for citizens, than dealing with chronic disease in adulthood. While policy and practice is moving in the right direction, redoubling efforts to ensure preventative interventions are in place in school and home settings is critically important," she added.

This ESRI research can be viewed here.