So far, evidence has not supported the effective use of abstinence-only sex education. It has been found to be ineffective in decreasing HIV risk in the developed world, and does not decrease rates of unplanned pregnancy.
According to SIECUS, the Sexuality Information and Education Council of the United States, an organisation that promotes comprehensive sex education in the United States, a "...study, conducted by Mathematica Policy Research Inc. on behalf of the U.S. Department of Health and Human Services, found that abstinence-only-until-marriage programs are ineffective." In 2007, the National Campaign to Prevent Teen Pregnancy published an overview of policy and research on "programs designed to prevent teen pregnancy and STD/HIV" titled Emerging Answers 2007. The report included a comprehensive metastudy examining research on the efficacy of abstinence-only as well as comprehensive sex education. Despite two less rigorous studies suggesting that abstinence programs may have some positive effects on sexual behavior", Emerging Answers concluded that "studies of abstinence programs have not produced sufficient evidence to justify their widespread dissemination." In contrast, the report judged the evidence for comprehensive sex education favorably, finding it effective for a wide range of students.
A federally-funded University of Pennsylvania study published in the Archives of Pediatrics & Adolescent Medicine found that only one third of sixth- and seventh-graders who completed abstinence-focused programs had sex within the next two years, compared to nearly half of the students who attended other classes, including ones that taught combined abstinence and contraception. Critics pointed out that the abstinence program used in the study was not representative of most abstinence programs; it did not take a moralistic tone, encouraged children to delay sex until ready instead of until married, did not portray extramarital sex as inappropriate, and did not disparage contraceptives. The sample groups were also exclusively African-American and therefore not demographically representative of the entire population.
A 2010 report by the Guttmacher Institute pointed out that pregnancy rates for teens 15-19 reversed their decline in 2006, near the peak of the Abstinence Only campaign in the United States. Sarah Kliff of Newsweek pointed out that there was no corresponding "indication of an uptick" in teen pregnancy rates when abstinence-only sex education funding was increased during the Clinton years, but in fact a small decline. James Wagoner, president of the nonprofit group Advocates for Youth, blames the poor quality of Bush era abstinence-only programs as compared to abstinence-only programs under Clinton's administration for the difference in outcomes.