Abstinence-only programs which focus on behaviour can reduce sexual activity among preteens and as a result lower the risks of disease and pregnancy, according to a new study. Despite criticisms that abstinence-only sexual education is moralistic, ineffective and contains inaccurate information, there has been little long-term research done to test the effects of "intervention"-style programs in the United States, say researchers from the University of Pennsylvania and the University of Waterloo, in a study published on Monday in the American medical journal, Archives of Pediatrics & Adolescent Medicine.

The research could ostensibly be applied to teens across North America, said author John B. Jemmott. Instead of portraying sex in a negative light or forgoing the discussion of HIV and sexually transmitted diseases altogether -- which has lead to some criticisms about abstinence education in the U.S. -- "intervention"-style programs focus instead on discussions about behaviour.

In a two-year study that looked exclusively at Grade 6 and 7 African-American preteens -- because of their high risk for pregnancy and diseases, according to researchers -- 662 students in Philadelphia were asked to talk about their hopes and dreams, their attitudes about sex and peer pressure.

By asking the participants to discuss their perceptions about sex and abstinence, researchers say their program delayed teenage sexual activity when compared with a healthy-lifestyles program that did not address sexual issues.

The research found that in the two years after the program, 33.5% of participants in the abstinence-only program had had sexual intercourse, compared with 48.5% of those in the healthy-lifestyles group.

"Abstinence is a valuable goal because if you can delay the onset of sexual activity for two years, that's two years these adolescents don't get a sexually transmitted disease or get pregnant," said Mr. Jemmott, a psychologist at the University of Pennsylvania.

"If they're older when they have sex, they're more mature and more likely to use condoms."

The abstinence-only intervention program did not discuss condom use or safe sex practices, he added.

Another three sexual education programs were compared in the study, one which focused on safe-sex and another two which combined abstinence discussions with safe-sex information. The study showed that when compared with the healthy lifestyles program, the rates of teen sex remained about the same for all three programs, although multiple-partner sexual activity was reduced.

In an editorial, the journal editors Frederick P. Rivara, a doctor at the University of Washington and Alain Joffe, a doctor from Johns Hopkins University in Baltimore, said the study's findings must now be combined with other studies on the prevention of sexually transmitted infections and unintended pregnancy in adolescents.

"No public policy should be based on the results of one study," they wrote.

Mr. Jemmott said the goal of the study is not to advocate for abstinence until marriage, but to delay sexual activity in young people. He added that the intervention-style program used in the study is not available in American schools, but was conducted independently on the weekends.

The study was funded in part by the National Institute of Mental Health in the United States.