New York (PTI): Abstinence-only sex education courses are ineffective in curbing adolescent sexual risk-taking but comprehensive programs do work, especially in reducing teen pregnancy, a new study, published on Thursday, says.

The study, published in the Journal of Adolescent Health, concludes that teaching about contraception doesn't increase sexual activity or sexually transmitted diseases among teenagers.

Teaching abstinence-only failed to reduce teen pregnancy or to delay sexual initiation, the study says.

University of Washington researchers led by Pamela K Kohler examined teens' responses to a 2002 federal study, the National Survey of Family Growth.

The researchers found that teenagers receiving comprehensive sex education, including information about contraceptives, reported about half as many pregnancies as teens, who had received abstinence-only or no sex education.

"It is not harmful to teach teens about birth control in addition to abstinence," Kohler said.