But which method is best in sex education?

One of the ways in which the debate between supporters of abstinence and comprehensive approaches to sex education has been framed is in terms of which is the most effective.

Although at first glance the evidence can seem confusing, with claims coming from both groups about the proven effectiveness of programmes embodying their values, when only the most reliable studies are taken into account the position is clear 20. There is good evidence, from studies of programmes implemented in the US, UK and other European countries and countries in Africa and Asia 21 22 23 24 25 26 27 28, that comprehensive sex education can reduce behaviours that put young people at risk of HIV, STIs and unintended pregnancy. Studies have repeatedly shown too that this kind of sex education does not lead to the earlier onset of sexual activity among young people and, in some cases, will even lead to it happening later.

In contrast there is no such robust evidence for the effectiveness of abstinence education. Almost all the studies that have claimed to show any positive outcomes are not well-enough designed to sustain these claims 29 30 31 so it is not possible to infer whether they work or not from the research reports.
So, what does the research evidence show about the effects of abstinence-based approaches?

The research that is available currently shows at best mixed outcomes for abstinence-based approaches to sex education, benefiting some young people in the short term but placing them at greater risks later. For example, two studies suggest that for some young people making pledges to abstain from sexual intercourse until marriage does lead to delay in the timing of their first sexual intercourse. But these young people tend to hold strong religious beliefs and enjoy being an exclusive group among peers who do not take abstinence pledges. As the researchers note this means that pledging abstinence is not appropriate for young people who do not hold strong religious views and, moreover, if lots of young people are involved in making pledges (as using abstinence education as a method of sex education requires) the sense of being special will be dissipated 32. In addition, while an abstinence pledge may work for some groups of young people as a way of delaying when they have sexual intercourse, the majority still have sex before they are married and when they do they report using condoms less often than 'non-pledgers' and are more likely to substitute anal or oral sex for vaginal sexual intercourse 33 34.

In April 2007 a company called Mathematica Policy Research published the results of a Congressionally mandated evaluation of federally funded abstinence-based programmes in American schools 35. The investigation, which looked at four programmes offering a range of settings and strategies, found that rates of abstinence and unprotected sex in students who took part in the programmes were virtually identical to rates among students who had been randomly assigned to not take part. The ages at first sexual intercourse were also nearly identical, as were the numbers of sexual partners. It appears that the programmes had no impact on how the students behaved.

With regards to HIV prevention, a systematic review of all relevant studies 36, published in October 2007, concluded, "Evidence does not indicate that abstinence-only interventions effectively decrease or exacerbate HIV risk among participants in high-income countries; trials suggest that the programs are ineffective." Nevertheless the authors stressed the paucity of robust data and the need for more rigorous trials. They noted that most studies have been conducted among American youth, which may limit the generalisability of their findings.