According to new research from think tank Resolution Foundation (RF), members of Generation Z are more likely to call in sick to work than their older colleagues who belong to Gen X, thanks to a mental health crisis that’s “supercharged” by young women.

RF found that a third of people ages 18 to 24 suffer from what’s called a “common mental disorder,” or CMD. CMDs include diagnoses like depression, anxiety, and bipolar disorder. In 2000, only 24% of young people were diagnosed with a CMD.

RF’s research found that the increase is largely driven by a mental health crisis among young women — 40% of women in Gen Z report suffering from a CMD, compared to just 25% of men.

Researchers don’t know exactly what’s causing the prevalence of mental illness to increase so sharply. Some theories are that it could have to do with young people having less access to healthcare and public services. Others believe there might not actually be an increase in mental illness, but simply an increase in diagnoses because there’s less stigma around talking about mental health in younger generations. But the impact is real: RF found that the number of young people taking sick days due to mental illness has doubled in the last decade. In general, young people are now more likely to be absent from work due to illness than people who are 20 years older — and mental illness is driving that trend.

RF’s research also showed that Gen Z women are 1.6 times more likely than men to take time off due to their mental health. That’s a reversal of an earlier trend — in the 2010s, young men took more time off work due to illness than young women.

“Youth worklessness due to ill health is a real and growing trend; it is worrying that young people in their early 20s, just embarking on their adult life, are more likely to be out of work due to ill health than those in their early 40s,” RF researchers said.