In the early 1990s, with panic over the AIDS epidemic rising, hundreds of school districts began making condoms more accessible to students. The hope was to encourage students to practice safe sex and better protect themselves from sexually transmitted diseases.

A new research paper suggests that decision may have backfired. It finds that access to condoms in school led to a 10 percent increase in teen births. The effects were concentrated in schools that offered condoms with no required counseling. Those schools also saw that gonorrhea rates for women rose following the condom programs.

It's possible that teens did engage in riskier behavior with the condoms available. Or teenage girls might have decided to use the condoms — which have an especially high failure rate — instead of birth control pills, which are more effective at preventing pregnancy. The research paper isn’t able to answer why teen births went up in the areas where schools gave out free condoms. But it does call into question some of the unintentional side effects of making the contraceptive more freely available.

Large school districts started condom giveaway programs in the 1990s. They had faster increases in teen births.

A Colorado school district was the first to create a school-based condom program, in 1989. Other districts quickly followed when the country’s largest school district — New York City Public Schools — implemented its own program in 1991. The second-largest school district, the one that serves Los Angeles, followed suit in 1992.

Most schools made condoms available through a staff member, like a nurse or counselor. A much smaller number gave students access to condoms from baskets or vending machines.

And many schools requested students receive some level of counseling when requesting a condom, including instruction on the proper method of use and information about the contraceptive’s high failure rate (18 percent of regular condom users become pregnant within a year due to misuse).

Kasey Buckles and Daniel Hungerman, the study's authors, looked at the schools that made condoms available with and without counseling. They looked at the teen births in those places and compared them with the birth rates of two other groups: teen girls in places without school condom programs and slightly older girls (those ages 20 to 24) in the same location. They studied the last group to see whether trends diverged between similarly aged women when the condom distribution programs started.

In both cases, they saw that the teen girls in areas with school condom programs had 10 percent higher-than-expected birth rates. This change was concentrated among schools that gave condoms away without counseling.

"Programs with counseling may have seen no change or perhaps a decline in teen fertility," Buckles and Hungerman write.

They also found that rates of gonorrhea were higher among teenage girls in schools with condom programs, with an additional 2.43 cases per 1,000 women. Again, these effects were mostly concentrated in schools that gave away condoms without counseling.

Did teens engage in riskier behavior? Decide not to use birth control pills?

There are a handful of theories that can explain why teen birth rates were higher in places with school condom problems. And while this paper doesn't explore which theory is right, they’re interesting to run through while considering the public health lessons of this paper.

One theory is that condoms encouraged teenagers to engage in riskier behavior than they would have otherwise — with the condoms available, they could possibly decide to have sex in situations where they otherwise wouldn’t. This was a worry raised by social conservatives as condom distribution programs became more common.

One study of the Los Angeles School District found this wasn’t the case — it surveyed nearly 2,000 high school students before and after a condom distribution program and found no changes in their sexual behavior.

Another possible explanation is that teens didn’t look for better contraceptives. A teenage girl who may have asked her doctor about birth control pills, for example, could decide not to when she knew condoms were available at school.

Buckles and Hungerman also discuss one last theory: that when schools implemented their condom programs, they put less effort toward other teen pregnancy prevention programs. School officials might have felt like they had taken steps to address the problem and could turn their efforts elsewhere.

In any case, the results should inform how schools moving forward design condom access programs — and think about the right level of counseling that ought to come with them.

Watch: Why over-the-counter birth control is so necessary