Participation in sports during adolescence is considered a healthy behavior. The extent to which adolescent athletes engage in other healthful (or risky) behaviors is less clear, however. We conducted a systematic literature review following the PRISMA Statement to assess the frequency of risky behaviors among athletes in this age group. We searched the PubMed, PsycINFO and SCA Sociological Abstracts databases for observational studies published in English over the last twenty years on the frequency of selected risk behaviors (alcohol consumption, smoking behavior, use of illicit drugs, unhealthy nutrition, and doping) in adolescent athletes. Two independent reviewers selected articles following the PRISMA Statement. Behavior frequency was assessed as was comparability of study design and methods. When possible, meta- analyses were performed using data from subgroups of studies in which operational indicators were comparable. Seventy-eight articles met eligibility criteria. Although report of risky behaviors varied across studies, we observed overall, that studies tend to report higher alcohol use, less smoking, less recreational drug use, and more smokeless tobacco use in (high-involved) athletes. Considerable heterogeneity was noted in study design, definition of target groups and use of operational indicators (I² ranged from 93.2% to 100%). Especially the higher prevalence of using alcohol and smokeless tobacco needs more attention in interventions targeted to this group. Overall, greater consensus on methods used to assess risky behaviors in adolescent athletes.

• This is the first systematic review focusing on different health related risk behaviors of adolescent athletes aged ≤ 18 years from different countries.

• Health related risk behaviors such as alcohol consumption are common among recreational and elite adolescent athletes.

• Athletes were more likely to consume alcohol, smokeless tobacco, and steroids and less likely to smoke and to use marihuana than non-athletes.

• Studies show high heterogeneity in the operational indicators, statistical methods, and target groups. Therefore, greater consensus around key definitions and study methods is needed to advance knowledge.