August 21 (HealthDay News) -- One reason why abstinence-only programs don't do much to prevent teen sexual activity is because abstinence can mean different things to teens than it does to adults, according to a University of Washington study.

Teens' attitudes and intentions about sex are more powerful than their attitudes and intentions about being abstinent, the researchers found.

"Interventions that have been created to encourage abstinence have treated abstinence and sexual activity as opposites. However, teenagers say they don't think of them as opposites," lead author Tatiana Masters, a doctoral student in social work, said in a university news release.

"These (abstinence-only) interventions are less likely to work than more comprehensive sex-education programs, because they are not meeting adolescents where they are, and they are speaking a different language," Masters said.

The study included 365 adolescents (230 girls, 135 boys) in Seattle who took part in an intervention to reduce HIV risk behavior. The participants filled out questionnaires asking them about their attitudes and intentions about abstinence and sex, and about their sexual activity in the previous six months.

At the start of the study, 11 percent of the boys and 4 percent of the girls had had sexual intercourse. That increased to 12 percent of the boys and 8 percent of the girls six months later, and to 22 percent of the boys and 12 percent of the girls one year later.

"This paper demonstrates that increasing abstinence intention does not lead to less sex. In fact, when abstinence intention and sex intention interact with each other a teenager is more likely to have sex," Masters said.

The study was published in the journal Perspectives on Sexual and Reproductive Health.

In 2007, the U.S. government provided $176 million for abstinence-only programs, but there is no federal funding for comprehensive sex education programs. This study's findings "raise serious concerns about the abstinence-only approach as a risk-reduction method for adolescent sexual behavior," Masters and colleagues concluded.

SOURCE: University of Washington, news release, Aug. 6, 2008