Adolescent sexuality is a relevant public health issue, as it affects risk to contract HIV and other
sexually transmitted infections. The assessment of prevalence of sexual intercourse among
adolescents may guide policies and programmes aimed at reducing the transmission of sexually
transmitted infections among this age group. Using data from the Thailand Global School-Based
Student Health Survey (GSHS) 2008, we assessed the prevalence of sexual intercourse in the
last 12 months and its associated factors among adolescents (N = 2758). Overall the prevalence
of sexual intercourse in the past 12 months was 11.0% (14.6% males and 7.6% females).
Variables positively associated with the outcome in multivariable analysis were male gender
(OR = 1.66; 95% CI 1.14–242), older age, =15 years (OR = 2.60, 1.80–3.74), current alcohol use
(OR = 2.22, 1.46–3.36), psychosocial distress (OR = 2.11, 1.44–3.09) and among females current
smoking (OR = 5.47, 1.62–18.48), lifetime drug use (AOR = 4.35, 1.04–18.3) and lack of parental
or guardian bonding (AOR = 0.51, 0.27–0.97). Efforts to control unhealthy lifestyles (substance
use) and psychosocial distress may impact on adolescents’ sexual activity