A Cochrane review ¹ included 39 studies with a total of 37,724 subjects. All included studies enrolled ethnically diverse youth in the US. Median final follow-up occurred 12 months after baseline. Programs took place in schools (10), community facilities (24), both schools and community facilities (2), healthcare facilities (2), and family homes (1). Results showed no evidence that abstinence-plus programs can affect self-reported sexually transmitted infection (STI) incidence, and limited evidence that programs can reduce self-reported pregnancy incidence. Results for behavioral outcomes were promising; 23 of 39 evaluations found a significantly protective intervention effect for at least one behavioral outcome. Consistently favorable program effects were found for HIV knowledge.

Comment: The quality of evidence is downgraded by indirectness (the homogeneity of the trial populations) and the probable self-reporting bias.