Methods: Cross-sectional analysis of data collected by the Irish Health Behaviours in School-aged Children national representative study, comprising 2,985 children aged 15-18 years. This paper focuses on age of relationships between early onset of smoking and substance use, violence and aspects of negative health.

Results: The average age of age initiation was 13.1 (SD 7.7). Early onset of smoking was found to correlated to early onset of drinking (r=0.425, p<0.001), of cannabis use (r=0.358, p<001) and of sniffing glue (r=0.142, p<0.001). Early age of onset was also found to be with bullying (r=-0.110, p<0.001) and fighting (r=-0.150, p<0.001). Injury, emotional and physical symptoms were not found to be associated with injury.

Conclusions: Smoking is a behaviour within a cluster of risk behaviours in which adolescents are involved. These analyses reiterate findings from previous studies but also suggest the younger the onset of smoking behaviour the higher the risk for involvement in substance use and in violent behaviour. Findings from the study re-emphasise the importance of prevention efforts targeted at young children, if not to prevent smoking altogether, then to delay the onset of this behaviour.