Adolescence is a period of exploration and experimentation that includes risk behaviours
such as substance use. Adolescents living in a situation of vulnerability could be more prone
to use substances. In this cross-sectional study, we aim to evaluate the association between
level of vulnerability and substance use considering explanatory factors. Data were obtained
from the first wave of the GenerationFRee project (www.generationfree.ch), a longitudinal
study based on data collected yearly between 2014 and 2019 on youth aged 15-24 years in
high- and professional schools. The sample included 5179 participants. We designated 4
risk behaviors: current tobacco smoking, alcohol misuse, cannabis use and other illegal drug
use. We defined vulnerability based on 3 criteria: relationship with parents, school
performance and socioeconomic status (SES) of their family. According to this definition,
participants were divided into three groups: No vulnerability, Moderate vulnerability and High
vulnerability. Each substance was compared by vulnerability level and controlled with
explicative factors such as age, gender, perceived health, emotional wellbeing, academic
track, nationality, living with parents, residence, family structure, money earned, and
perceived own financial situation. Results show that all substances but alcohol misuse are
associated to vulnerability at the bivariate level. All the explicative factors were also
significant with the exceptions of academic track and amount of money earned per month.
In the multinomial regression, for the Moderate and High vulnerability groups, cannabis use
was the only behaviour that remained significant. In conclusion, this study shows an
association between level of vulnerability and substance use, especially cannabis use. Our
results also reveal the complexity around vulnerability and how the interaction with social
aspects influence it. However, it also shows that with three simple questions about parents,
school and SES, healthcare providers can identify youths more at risk of vulnerability and,
consequently, of using substances.