The use of alcohol, tobacco, and marijuana in Chile and the rest of the world is a public health problem, particularly in adolescence. A recent survey showed that the prevalence of Chilean adolescents’ consumption (7th to 12th graders, 12-18 years old) was 31.1% for alcohol, 33.4% for tobacco, and 30.9% for marijuana in the last month. Moreover, this survey indicated a high precocity in consumption, with an onset before the 15 years, in which nearly half of adolescents report having used one of these substances at least once in their lives (Servicio Nacional de Alcohol y Drogas (SENDA), 2017). Adolescence is a critical period when many youths begin to experiment with alcohol, tobacco, and marijuana (Johnston, O’Malley, Bachman, & Schulenberg, 2010). The first approach to alcohol, tobacco and marijuana is usually between 12 and 15 years old. The habits and consumption generated in adolescence are crucial because they can determine the health and well-being trajectories throughout the life cycle. The latest research has emphasized the importance of deepening the study of relational factors related to substance use other than the family. Peers’ substance use appears as one of the main predictors of adolescents’ consumption (Macdonald-Wallis, Jago, & Sterne, 2012; Neff & Waite, 2007) as peer group become a central reference during adolescence (Gaete, 2015).

Although the relationship between peer relationships (e.g., friendships) and substance use have been stressed in the literature, there is no studies in Chile that examine it from a longitudinal social network perspective. Adopting this approach allow not only differentiating the effect of substance use on friendship (selection) to the effect of friends on adolescents’ substance use (socialization), but also analyzing individuals’ characteristics that could moderate peer socialization on substance use, and even studying substance use as a relational behavior (i.e., as a consumption network between two or more adolescents) instead of merely as individual behaviors. Consequently, focusing on this peer dimension and adopting a social network perspective allows a deeper understanding of this phenomenon and potentially identifies new lines of prevention and intervention that decrease the risk of consuming alcohol, tobacco, and marijuana.

The present study analyzes the interplay between peer relationships and adolescent substance use by examining secondary network data from Chilean, Colombian, Italian, and Dutch schools (approximately 4700 6th-10th graders from 90 classrooms). The analysis plan contemplates three longitudinal social network studies: Specifically, it will analyze the effect of substance use (alcohol, tobacco, marijuana) in the selection of friendships relationships, and the effect of friendships on substance use (peer socialization) (study 1); examine the moderation effect of susceptibility to peer pressure and depression in peer socialization of substance use (study 2); and identify the factors the leading to the formation and maintenance of drinking and smoking networks (study 3).

This study will be the first of using cutting-edge longitudinal network analyses analyzing the effects of peer relationships on substance use in Chilean adolescents. Moreover, it will test the moderating effect of susceptibility to peer pressure and depression in peer socialization of substance use. It will also be the first study to analyze drinking and smoking as network variables and the factors that predict the formation of these types of networks. As the analyses will assemble network datasets from different countries (Chile, Colombia, Italy, and the Netherlands), this project will allow the comparison between countries with diverse income levels and observe whether peer mechanisms on substance use operate similarly or not. There is a growing recognition of the benefit of using social networks in behavioral interventions (Campbell et al., 2008; Valente, 2017), and interventions that are based on a detailed understanding of the complex social system of adolescents would be more effective. The results with a focus on peer selection and socialization should inform practitioners and policymakers in their design and delivery of effective educational and health prevention programs but may certainly be of interest to broader policies on substance use. Finally, this project will generate and consolidate international and national collaborations with renowned scholars on peer relationships and substance use.