It’s arrested development.

Today’s teens are growing up more slowly than their predecessors, new research suggests — meaning they’re less likely to engage in classically “adult” activities like working for pay, dating, having sex, drinking alcohol, driving and going out without their ’rents. The study, recently published in the journal Child Development, dubs this trend a “slow life strategy.”

“The developmental trajectory of adolescence has slowed, with teens growing up more slowly than they used to,” lead author Jean M. Twenge, a professor of psychology at San Diego State University, said in a statement. “In terms of adult activities, 18-year-olds now look like 15-year-olds once did.”

In other words, according to co-author Heejung Park of Bryn Mawr College, the study suggested “teens today are taking longer to embrace both adult responsibilities (such as driving and working) and adult pleasures (such as sex and alcohol).”

Meanwhile, adolescents’ apparent decline in working for pay suggests their parents will increasingly have to pony up. The projected cost of raising a child born in 2015 from birth to age 17 — not including college — totals $233,610 for a middle-income American family, according to the U.S. Department of Agriculture’s annual Expenditures on Children by Families report released in January. And kids get more expensive the older they get: Annual expenses were about $300 less for kids two and under, on average, and $900 more for kids aged 15 to 17.

The present research, using seven nationally representative surveys of about 8.4 million people aged 13 to 19 between 1976 and 2016, compared teens across decades based on how they said they used their time. The so-called “adult activities” were less common during periods when median income was higher, life expectancy was greater, women were older during their first birth, and college enrollment came later — and when communicable disease prevalence and family size were lower.

The findings likely aren’t a product of time spent on extracurriculars or homework, the authors wrote — but “may or may not be linked to increased Internet use.”