Alcohol use, cigarette smoking, vaping and number of sexual partners: A cross-sectional study of sexually active, ethnically diverse, inner city adolescents.

Context: There are few UK data on the prevalence and clustering of risky behaviours in ethnically diverse adolescents.

Objectives: To investigate the prevalence of reported alcohol use, smoking and vaping, and explore whether these behaviours are associated with increased numbers of sexual partners.

Design: Questionnaire survey of 'Test n Treat' chlamydia screening trial participants.