Quantification of the influence of friends and antisocial behaviour in adolescent consumption of cannabis using the ZINB model and data mining.

Cannabis is the most consumed illegal drug in Europe and its repercussions are more important when taken up at an early age. The aim of this study is to analyse and quantify the predictive value of different personal, family and environmental variables on the consumption of cannabis in adolescence. The sample is made up of 9284 adolescents (47.1% boys and 52.9% girls) with an average age of 15.59 years (SE=1.17). The ZINB model highlights, as factors that increase the number of joints consumed per week, consumption by the peer group, nights out during the week, gender, the production of forbidden behaviour and the use of other substances, whereas the risk factors for the consumption of cannabis are consumption by friends, ease of access, production of forbidden behaviour and the use of other substances. Association rules highlight the relationship between cannabis consumption, ease of access, production of forbidden behaviour and tobacco consumption. Finally, decision trees enable us to predict cannabis consumption as well as the number of joints an adolescent will consume per week based on the production of forbidden behaviour, consumption of other substances and number of friends who consume cannabis. The results of this work have practical implications concerning the prevention of cannabis consumption in an adolescent population.