The latest version of the Centers for Disease Control and Prevention’s biannual report on teen shenanigans, the Youth Risk Behavior Surveillance System, has revealed that high school-aged Americans are having less sex than at any point since the assessment project began nearly 20 years ago.

Based on 15,000 surveys filled out by teens at 144 schools in all states except for Oregon, Washington, Wyoming, and Minnesota in 2017, about 40 percent of US students have engaged in sexual intercourse with a partner of the opposite or same sex – in 1991, the figure was 54 percent.

Yet before we tip our hats to the current adolescent generation’s apparent improvement in decision-making compared to their predecessors, the comprehensive, 479-page study quickly points out that the proportion of sexually active individuals who are using condoms is almost 10 percent lower than the rate found in 2005 (53.8 vs. 62.8 percent).

According to the research team, use of condoms – the only birth control method that also protects against sexually transmitted infections – was on a promising upward trajectory from 1991 (46.2 percent) to 2005. But then, frustratingly, it began to decline. Beginning that same year, the percentage of teens who had ever been tested for HIV began to drop as well (11.9 to 9.3 percent). The proportion of sexually active teens not using any method to prevent pregnancy, an obviously risky behavior, thankfully did decline between 1991 and 2007 (17 to 12 percent) but has since remained steady instead of continuing to improve.

“The more kids know about it, the less mystique there is about it, [thus] the more they want to wait,” Cora Breuner, a pediatrician and chair of the American Academy of Pediatrics Committee on Adolescence, speculated to Science News about the cause of the reduced sex pattern.

“I’m actually more concerned about the lack of condom use,” she added, attributing this phenomenon to the increasing popularity of long-acting contraceptives, such as IUDs and dermal implants and less fear of HIV.

“We are not doing a good job informing kids about protecting themselves from getting sick with infections that can last the rest of their lives and have significant negative outcomes, including infertility and even death.”

Other highlights (and worrying lowlights) from the report, which quantifies trends in six categories of adolescent health, include:

- The rate of cigarette smoking is down by two-thirds since 1991; 8.8 percent of high school students had smoked cigarettes on at least 1 day during the 30 days before the 2017 YRBSS survey, compared with 27.5 percent in the first survey.

- Almost 40 percent of driving teens admitted to texting or emailing behind the wheel in the last 30 days.

- Only 16 percent had ridden in a car with a driver who had been drinking, the rate was 40 percent in 1991.

- 43 percent used a computer for 3 or more hours per day on an average school day for something that was not school work.

- Almost 15 percent were obese and 16 percent were overweight.

- In the year prior to the survey, 19 percent reported that they had been bullied and 7.4 percent had attempted suicide. Earlier this month, another CDC report found that suicide rates among 10- to 19-year-olds have risen 56 percent from 2007.