Humans, it would appear, like having sex. A review of research into the effects of preaching abstinence as a way to avoid unwanted pregnancies and sexually transmitted diseases in the US has concluded that they do not work.

While adolescents may want to remain virgins until their wedding day, they tend to succumb to temptation with potentially adverse consequences that might have been avoided had they had some more practical sex education, according to experts.

However, despite people increasingly leaving marriage until later in life, the number of schools in the US teaching students about sexuality and birth control has slumped in recent years.

Congress spent more than $2bn on programmes to support the idea of abstinence between 1982 and 2017, while the US has spent a total of $1.4bn in foreign aid designed to prevent HIV by persuading people not to have sex, the researchers noted.

US states are banned from using their funds to educate adolescents about contraception – except to stress its failure rates.

Writing in the Journal of Adolescent Health, a team of experts from the US and UK said: “Adolescence is marked by the emergence of human sexuality, sexual identity, and the initiation of intimate relations; within this context, abstinence from sexual intercourse can be a healthy choice.

“However, programmes that promote abstinence-only-until-marriage (AOUM) or sexual risk avoidance are scientifically and ethically problematic and as such have been widely rejected by medical and public health professionals.

“Although abstinence is theoretically effective, in actual practice, intentions to abstain from sexual activity often fail.”

In the 1960s, the average American woman had sex for the first time at 19 but this age fell progressively until the early 1990s when it hit 17, before rising again to 17.8 in 2005 when it levelled off. The average woman currently gets married at 26.5 years.

The average age for first-time sex for men is 18.1 years with first marriage at 29.8 years, a gap of 11.7 years.

“Only a small percentage of young people wait until marriage to have their first intercourse,” the researchers said.

“In contrast, among women born in the 1940s … the interval between first intercourse and first marriage was between one and 1.5 years.”

The researchers pointed to previous reviews of programmes designed to encourage sexual abstinence, including one in 2007 which found they “consistently showed no impact on sexual initiation, frequency of vaginal sex, number of partners, condom use, or the incidence of unprotected vaginal sex”.

Another in 2012, by the US Centers for DiseaseControl and Prevention, examined 66 comprehensive risk reduction (CRR) sexual health programmes and 23 abstinence programmes.

“CRR programmes had favourable effects on current sexual activity (ie, abstinence), number of sex partners, frequency of sexual activity, use of protection (condoms and/or hormonal contraception), frequency of unprotected sexual activity, STIs and pregnancy,” the researchers wrote.

“In contrast, the meta-analysis of risk avoidance (AOUM) programmes found effects on sexual activity, but not on other behaviours. (Equivocal changes were found for a decrease in frequency of sexual activity and an increase in pregnancy.)”

The idea that abstinence was “the only certain way to avoid out-of-wedlock pregnancy, sexually transmitted diseases (STDs), and other associated health problems” was a “misleading and potentially harmful message”.

This was because it “conflates theoretical effectiveness of intentions to remain abstinent and the actual practice of abstinence”, the researchers said.