(Reuters Health) - Teens who start drinking at younger ages are more likely to have their first sexual encounter earlier than others, according to a new study.

Although the pattern held true for both genders, the effects were more pronounced for younger females.

“Adolescents who engage in early sex have higher risks for sexually transmitted infections or unplanned pregnancies,” lead study author Dr. Kelly Ann Doran of Indiana University in Bloomington told Reuters Health by phone. “Although the U.S. has seen a drop in pregnancy rates, we still have one of the highest in the Western industrialized world. It’s a big issue, and it’s important to find the risk factors that lead to risky sex.”

Doran and colleagues analyzed survey data from 4,079 males and 4,059 females who participated in the National Longitudinal Study of Youth 1997. Data collection started when participants were between ages 12 and 16, and it continued periodically until they were 25 to 31 years old.

On average, boys and girls both had their first drinks before their 15th birthday. The average age for first sexual encounter was 16 for both genders, the study authors wrote in the Journal of Adolescent Health.

Onset of drinking before age 14 more than doubled the odds that adolescents of either gender would have earlier sexual encounters. For females who had their first drink at 13 or younger, the likelihood of early sexual initiation quadrupled.

“The association is strong for both males and females,” Doran said. “It still holds (regardless of) socioeconomic status or poor parental monitoring, which could mean we see a unique risk with early drinking.”

“With research, we sometimes think about all of these different risks as separate and have separate programs for alcohol use or teen pregnancy, but many of these behaviors are interconnected,” said Dr. Arielle Deutsch of Sanford Research in Sioux Falls, South Dakota. Deutsch, who wasn’t involved with this study, has researched the link between substance use and sexual intercourse among teens. [

“We have to really think about all of these behaviors and what adolescents may be going through during this time in their lives,” she told Reuters Health by phone.

Future studies should look at the reasons why early drinking may be linked to earlier sex, such as lowered inhibitions, impaired decision-making, and peer pressure among social groups, Doran said.

“Impairment from alcohol increases the likelihood of being victimized or victimizing other people,” she said. “We’d like to do more research to see if there is any difference for voluntary or involuntary sex as well.”

The emotional and social context around the first-time sex experience is important, too, Deutsch added.

“It’s about the relationship between two people and how individuals think about what they’re doing,” she said. “How do teens think about planning their first sexual experience?”

“When teens talk about things like drinking, sex, hanging out with their friends, and partying, it’s all interconnected, especially with parenting approaches,” Deutsch said. “We should be talking to teens about how to make good choices overall and have the experiences they want in life.”

SOURCE: bit.ly/2wT9O7X Journal of Adolescent Health, online August 19, 2017.