Background:

• Early adolescence is a critical period usually associated with substances experimentation. In Tunisia, some studies were carried out recently to evaluate tobacco and cannabis use in the colleges and high schools. However, few studies were led in the middle schools. While onset of substances use usually occur during early adolescence.
• Aims: To evaluate the prevalence of tobacco and cannabis use and to determine if there is an association between their use among the young adolescents of Sousse.

Methods:
A cross-sectional study was conducted in the region of Sousse, Tunisia during the 2013/2014 school year among a proportional and stratified sample of 4272 schoolchildren randomly selected in 16 public middle schools from the region of Sousse. Data about sociodemographic characteristics, tobacco products and cannabis use among the schoolchildren, their parents, their siblings and their friends were collected using a self administrated questionnaire.

Results:
Females represented 50.5% (2157) of participants. The mean age of schoolchildren was 13.3 ±1.2 years. Among participants, 12.9% (CI_95%: 11.9%-13.9%) reported lifetime tobacco use, 4.5% (CI_95%: 3.9%-5.1%) were current cigarette smokers, 3.2% (CI_95%: 2.7%-3.7%) were current water pipe users and 1.9% (CI_95%: 1.5%-2.3%) reported lifetime cannabis use. The age of tobacco use onset (11.2 ±2.7 years) was significantly inferior to the age of cannabis use onset (13.1±2 years) (p< 0.001). The most influential risk factor on cannabis use was current cigarette smoking with an adjusted odds ratio of 7.3 (CI_95%: 4.2-12.5).

Conclusions:
National school-based substances use prevention program is required in Tunisia. Tobacco use prevention deserves more efforts as it is a gateway to other substances use such cannabis.