Determinants of the intention to abstain from or reduce alcohol, tobacco or cannabis use among 15-25 year-olds

Objective: This study was designed to identify the sociodemographic and psychosocial factors (based on the theory of planned behaviour) associated with the intentions of young people to remain non-smokers and refrain from experimental cannabis use, and their intentions to reduce drinking during a party, quit smoking and reduce cannabis use among users. Methods: 3,652 young people aged 15 to 25 years were interviewed by means of an on-line questionnaire. The sample was recruited from an internet access panel and constructed according to the quota method applied to the following variables: gender, age, region, habitat and head of family occupation. Results: Each of the psychosocial determinants (attitudes, norms and control) helped to explain the subject's intention not to smoke and/or use cannabis. The presence of a prohibition norm in the family was also associated with a decreased intention to experiment with cannabis. Among substance users, attitude determined the intention to quit or reduce the use of the three substances (tobacco, alcohol and cannabis) and control was involved in the intention to reduce drinking and quit smoking. Finally, norms only influenced the intention to reduce drinking during parties. Conclusion: This study demonstrates the importance of considering psychosocial factors to explain health behaviours and to identify and propose interventions. These results support the priority given to smoking prevention, justify the value of early interventions and confirm the importance of considering social inequalities in health when developing prevention programmes.