Teenagers who don’t get enough sleep may be at an increased risk of engaging in unsafe sexual behaviors, such as not using condoms or having sex under the influence of alcohol or drugs, according to new research published by the American Psychological Association.

“Teens by and large are not getting the recommended 8 to 10 hours of sleep a night, due to a number of reasons, including biological changes in circadian rhythms, early school start times, balancing school and extracurricular activities, and peer social pressures,” says Wendy M. Troxel, PhD, a RAND Corporation senior behavioral and social scientist and lead author of the study published in the journal Health Psychology, in a release. “Insufficient sleep may increase the potential for sexual risk-taking by compromising decision-making and influencing impulsivity.”

Troxel and her co-authors, all from RAND Corporation, a nonprofit, nonpartisan research institution, analyzed data from a large, long-term study of 1,850 racially and ethnically diverse adolescents and young adults in Southern California. The data were collected four times between 2013 and 2017. Participants were, on average, 16 years old in 2013 and 19 years old in 2017.

The teens reported their sleep schedules on weekdays and weekends and whether they had trouble sleeping in the four weeks prior to filling out the survey. The participants also reported whether they used alcohol, marijuana, or other drugs right before or during sexual activity and whether they used condoms.

The teens were grouped based on their sleep patterns over the four-year period, including weekday sleep duration, weekend sleep duration, differences in sleep patterns between weekdays and weekends, and sleep quality.

The majority of teens were classified as intermediate weekday sleepers, who got an average of 7.5 hours of sleep per school night, which is below the recommended sleep duration for this age group. There was also a group of teens, called short weekday sleepers, who got well below the recommended sleep duration, with 6.35 hours per school night. Only 26% of teens could be classified as sufficient weekday sleepers, averaging about 8.5 hours per night, according to Troxel.

As for the weekends, most teens in the study were intermediate weekend sleepers, clocking in just over 9 hours, while long weekend sleepers netted an average of 10.6 hours and short weekend sleepers got an average of 7.8 hours, says Troxel.

Previous research has shown that irregular sleep patterns (such as sleeping in on weekends) can put teens at risk for negative health outcomes. Therefore, Troxel and her colleagues expected that teens who slept in on the weekends to make up for lost sleep during the week would show greater sexual risk-taking than those who had a more consistent sleeping routine.

Contrary to what they predicted, the researchers found that adolescents who were short weekday and short weekend sleepers (ie, those who consistently did not get enough sleep) were nearly two times more likely to engage in unsafe sex than those who slept in, on average, an extra 3.5 hours on weekends.

“Teens who were short weekday and short weekend sleepers were not getting adequate sleep during the school week and were not catching up on sleep on the weekends, and thus were chronically sleep-deprived,” says Troxel.

The researchers did not find that sleep quality had any effect on risky sexual behavior.

While this study could not make a direct link between sleep quality and sexual behaviors, it adds to a growing body of research about the potential role of sleep disturbances and adolescent risk-taking behaviors, Troxel says.

“Sexual risk-taking in adolescence poses serious health concerns, such as an increased potential of getting sexually transmitted infections, including HIV,” she says.

Troxel acknowledged that the findings pose a significant challenge for parents, clinicians, and policymakers.

“On one hand, we should encourage sleep routines for teens because regularity is important for maintaining healthy sleep and circadian rhythms,” she says. “However, for most US teens, whose weekday sleep opportunities are constrained due to early school start times, maintaining consistency in sleep-wake schedules throughout the week may not only be unrealistic, but also may be unhealthy, if it perpetuates a pattern of chronic sleep deprivation.”

Troxel suggests possible strategies that may help teens get the sleep their bodies need.

“Our recommendation is for parents and teens to find a middle ground, which allows for some weekend catch-up sleep, while maintaining some level of consistency in sleep-wake patterns,” she says. “We also need to encourage school districts to consider delaying school start times because this could make a substantial difference in helping teens get adequate sleep.”