Adolescent substance abuse (SA), which includes the consumption of alcohol, cigarette smoking, the consumption of drugs and other behaviors, is a significant public-health issue in the world today. Recent data showed that prevalence of SA among adolescents in Croatia and surrounding countries (i.e. former Yugoslav republics) is alarming and needs serious intervention. It is hypothesized that participation in physical-exercise-and-sport (PE&S) will reduce the tendency of young people to abuse substances. However, the literature to date has not consistently validated the perception PE&S factors are factors which could buffer SA among children and adolescents. One of the probable reasons for evident inconsistencies on findings about relationship between PE&S and SA is a cross-sectional nature of studies done so far. Therefore, the main rationale (i.e. problem) of this study is lack of current knowledge about influence of the PE&S on SA among adolescents. The main objective of this study is to prospectively investigate the influence of PE&S on SA among adolescents aged 17 to 18 years old. Aims of the project are: (1) to define prevalence and trends of SA among adolescents aged 17 to 18 years old; (2) to define prevalence and trends of PE&S participation; (3) to establish interrelationships which exist between socio-demographic, psychological, educational-factors, and PE&S (predictors); (4) to identify multivariate and univariate associations between: socio-demographic and SA, psychological factors and SA, PE&S and SA, educational - scholastic factors and SA.Expected results of the project are: (1) definition of the prevalence of SA among adolescents; (2) definition of the adolescents' participation in PE&S; (3) identification and interpretation relationships which exist between and within studied predictors of SA (educational factors, socio-demographic factors, PE&S, psychological factors); (4) identification of the influence of studied predictors on SA.

Inclusion Criteria:

• Children involved in regular scholastic system

Exclusion Criteria:

• No

The sample will comprise approximately 1,000 participants (50% males). At the beginning of the study, the participants will be attending the 3rd year (grade) of high school, and therefore practically all subjects will be 17 years of age at the moment the study starts (+/- 6 months). Participants will be randomly selected from 10 to 15 high schools which offer a 4-year high school education. Because of the prospective study design and consequent need to repeatedly test the same participants, only those schools where the investigators already have personal and professional contacts with the school authorities will be used as possible test environments.