I am writing to respond to the Aug. 3 commentary by Melissa Bird of Planned Parenthood about how to promote sexual health and safety, especially among adolescents.

In her article, Ms. Bird suggests that abstinence-centered prevention programs are failing and that comprehensive (i.e., condom-centered) sex-education programs are succeeding. Yet in recent testimony before a congressional hearing called by Rep. Henry Waxman, strong scientific evidence to the contrary was presented. Out of 115 scientific studies of sex-education programs over the past 15 years, no comprehensive sex-education program was found to increase consistent condom use by teens for a period of at least one year, nor were any shown to reduce teen sexually transmitted diseases for a one-year period of time. In contrast, five abstinence education programs were found to significantly reduce teen sexual activity for one year after program participation.

Two additional studies have also been published recently that found abstinence programs had reduced the onset of teen sexual activity by 50 percent after a one-year period, and a third study found a significant decrease in sexual activity after two years.

These are important scientific findings that have not been well-publicized because they do not support a political or social agenda that is critical of abstinence education.

I have been conducting research in this field for 20 years. Several years ago, I led a nationwide study of the impact of Planned Parenthood clinics on rates of teenage pregnancy. We found that the teenage birthrate went down slightly in counties where a Planned Parenthood clinic opened up, but that the teen pregnancy rate increased significantly in those same areas. The slight reduction in teen births was achieved through a significant increase in abortions performed on teen girls, which offset the increase in pregnancies, rather than through increasing contraceptive use by teens. This study was published in a professional journal (Family Perspective, Vol. 20, No. 3) and the Wall Street Journal and was also presented before Congress.

After three decades of funding "comprehensive" sex-education efforts to persuade teens to use condoms, our nation has epidemic levels of teen STDs (one out of four adolescent girls in America has an STD, and the number is one out of two for black girls) as well as increasing levels of sexual violence among teens. The totality of scientific evidence leads me to conclude that the best prevention approach is a strong, undiluted abstinence education program for teenagers that is reinforced at regular intervals in grades 7 through 12. This is the best way to "keep teens healthy and safe," a goal that I share with Ms. Bird, a goal that is too often sacrificed to a political agenda that does not have the well-being of our youths as its top priority.

Stan E. Weed, Ph.D, is president and director of the nonprofit Institute for Research and Evaluation, headquartered in Salt Lake City.