Young adults aren't behaving the way their parents did: They're not drinking as much, they're facing more mental health challenges, and they're living with their parents longer. On top of that, computer games and social media have become a sort of stand-in for physical relationships.

All that means young Californians aren't having as much sex.

The number of young adults going without sex was rising even before covid-19 made dating harder and riskier. In 2011, about 22% of Californians ages 18 to 30 reported having no sexual partners in the prior 12 months. That crept up to 29% in 2019, and it jumped to 38% in 2021, according to the latest figures from UCLA's California Health Interview Survey.

Other age groups in California also reported an increase in abstinence, but the trend was not nearly as pronounced.

"Everything happens later," said San Diego State University psychology professor Jean Twenge, author of "Generations: The Real Differences Between Gen Z, Millennials, Gen X, Boomers, and Silents — And What They Mean for America's Future." She said the numbers reflect how young adults increasingly delay major life events, such as moving out of their parents' homes and forging long-term romantic relationships.

Singles saw the most dramatic change.

It has long been the case that single people are more likely to report having no sex than married or cohabiting people. But as young adults delay marriage, the gap has widened.

Young adults may be putting off long-term relationships "due to their increasingly economically precarious status or stress related to completing education and looking for jobs," said Lei Lei, a sociology professor at Rutgers who recently co-authored a paper that examined why fewer young adults are having sex. "They are busy with other domains of life." Researchers also noted that hundreds of thousands of young adults identify as asexual.

Rising computer use may play a role in the trend. Young adults increasingly form relationships through playing video games with people they do not physically meet, Lei said. These distant relationships sometimes interfere with the formation of sexual relationships.

A Pew Research Center report from 2015 found equal numbers of men and women played video games but that young adult men were more than three times as likely as young adult women to identify as serious "gamers."

Young adults also have access to endless amounts of free pornography online, a departure from the porn magazines, videotapes, and DVDs many of their parents bought. Much of the most popular online porn features violence or coercion, which gives some young adults a flawed perspective on sex and turns others off it entirely, said Debby Herbenick, director of the Center for Sexual Health Promotion at Indiana University Bloomington's School of Public Health.

"Those kinds of behaviors are really, really normalized among young people," she said, referring to rough sex.

Sex also has a correlation with income. Young adults who make less money were more likely to go without sex than peers making more.

Much recent discourse about lack of sex among young adults has revolved around so-called incels, young men who contend — often in vile, misogynistic terms — that dating apps like Tinder make it easier for women to find conventionally attractive, wealthy, or otherwise high-status men and ignore everyone else.

Erin Tillman, a certified sex educator and executive director of the nonprofit Sex-Positive Los Angeles, said it makes her sad when she hears men blame women for not wanting to have sex with them. She said those men could likely change their perspective and find intimacy.

"They hold the cards in terms of making themselves better," she said.

The sexless trend has the potential to lower rates of unplanned pregnancy. And it could also reduce the spread of sexually transmitted infections, though that has not yet happened.

Herbenick does worry about young adults who want sex but aren't having it. "It can feel really lonely if you feel like people are rejecting you or wouldn't be interested in you," she said.

But Tillman remains optimistic, noting the latest group of young adults, like every new generation, is finding its way and approaching sex differently than their parents.

"I'm not worried, because people are just basically finding different ways to connect with each other," Tillman said.

Phillip Reese is a data reporting specialist and an assistant professor of journalism at California State University-Sacramento.

This article was produced by KFF Health News, which publishes California Healthline, an editorially independent service of the California Health Care Foundation.