Young men and boys who receive sex education before age 18 are more likely than others to use more than one type of contraception, such as a condom in addition to their female partner’s hormonal birth control, according to a small study.

“The dual method significantly decreases the chances of contracting a sexually transmitted infection (STI) or having an unplanned pregnancy,” said lead author Nicole Jaramillo, a public health researcher at San Diego State University.

“This is especially important among adolescent males with the growing use of long-acting reversible contraception (LARC) methods among their female partners,” she said. “It is still very important to promote and educate about the use of condoms for STI prevention.”

Jaramillo and colleagues looked at data from 539 heterosexual boys and men, 15 to 20 years old, who answered the 2011-2013 National Survey of Family Growth and reported being sexually active. The survey asked whether they had received sex education about seven topics: STIs, HIV/AIDS, how to say no to sex, birth control methods, where to get birth control, how to use a condom, and abstinence.

The survey also asked about contraceptive use during their last sexual intercourse, including whether they had relied only on female-controlled methods such as the pill or LARC, relied only on male-controlled methods such as vasectomy or condoms, used a combination of contraceptive methods or used no method.

Almost all of the participants — 99 percent — said they had received sex education on at least one topic, and 19 percent said they had learned about all seven. Most learned about STIs (95 percent) and HIV/AIDS (92 percent). The least commonly taught topic was where to find birth control, with less than 42 percent saying they had received such instruction.

Most, 91 percent, reported using contraception. Condoms alone were used by almost 44 percent, almost 9 percent had relied on female-only methods and 39 percent used dual methods.

Having learned about birth control methods and how to say no to sex were associated with dual-contraception use. With exposure to each additional sex education topic, the odds of using dual methods increased by 47 percent, researchers found.

“This study allowed us to look at the different topics of sex education rather than grouping the topics as ‘abstinence only’ versus ‘comprehensive’ sex education,” Jaramillo said. “Sex education that focuses on a broad range of topics is the most effective form of sex education.”

In the United States, STI rates have increased in recent years, Jaramillo added. In 2013, about 20 million Americans contracted an STI, with about half of the cases among people age 15 to 24, according to the Centers for Disease Control and Prevention. In addition, chlamydia, gonorrhea and primary and secondary syphilis cases rose to an all-time high in 2015, the authors write in Journal of Adolescent Health.

U.S. rates of STIs and unintended pregnancies are among the highest in industrialized countries, the study team notes. However, U.S. teen birthrates have dropped to an all-time low of 24 births per 1,000 girls and women between ages 15 and 19, according to CDC data.

“We know young men play a key role in making decisions about contraceptives, but not many reproductive health programs target them,” said Jennifer Manlove, a reproductive health researcher at Child Trends in Bethesda.

“We know from other research that high-quality programs are engaging, interactive and targeted toward the population,” said Manlove, who was not involved in the study. “Programs should highlight men’s role in contraception.”