Most of us would now start with a search for a systematic review on the subject.
Observational studies conclude that interventions work.
Randomised trials demonstrate that they do not. Eleven computerised databases were searched, eight journals hand searched, and reference lists reviewed of all relevant papers. Included were randomised and observational studies on adolescents 18 years or less and evaluating primary prevention programmes with outcomes of start of sexual intercourse, birth control use or responsible sexual behaviour. Randomised studies were not significantly different for any outcome. For responsible sexual behaviour and birth control use odds ratios greater than 1 indicate a desirable effect of intervention.