People in their early 20s are more likely to be not working due to ill health than those in their early 40s, a report has found.
This is "radically different" from the past, the Resolution Foundation said, when the older you were the more likely you were to not work due to sickness.
Poor mental health among young people is on the rise, official figures show.
This can hamper their education and lead to them being in lower-paid jobs or unemployed, the report said.
One in 20 young people (5%) were economically inactive due to ill health in 2023, it said.
According to the report, young people now have the poorest mental health of any age group - a reversal from two decades ago when they had the lowest incidence of common mental disorders.
In 2021/22, 34% of young people aged 18 to 24 reported symptoms of a mental disorder, such as depression, anxiety or bipolar disorder.
In 2000 that figure stood at 24%.
As a result, more than half a million 18 to 24 year olds were prescribed anti-depressants in 2021-22.
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Louise Murphy, senior economist at the Resolution Foundation, said attention had more often been on mental health in higher education, but "what should most worry us is when poor mental health comes together with poor education outcomes".
"The economic consequences of poor mental health are starkest for young people who don't go to university, with one in three young non-graduates with a common mental disorder currently workless," she said.
The study found that young women fare worse, and are one-and-a-half times more likely to experience poor mental health as young men (41% compared with 26%).
The research also found that 79% of 18 to 24 year olds who are "workless" due to ill health only have qualifications at GCSE level or below.
This compares with 34% of all people in that age group.
If children aged 11 to 14 suffer poor mental health they are three times more likely not to pass five GCSEs including English and Maths compared with healthy children, the report said.
Off the back of the study the Resolution Foundation, which campaigns for better living standards for those on low and middle incomes, is calling for better mental health support in colleges and sixth forms, and for more to be done to make it so that less young people leave compulsory education with low qualification levels.
The research has been produced by the Resolution Foundation, but is funded by the Health Foundation - a charity which says it aims to bring about better health and care.
The director of the Health Foundation, Jo Bibby, said that the "building blocks of health" are things like "good employment and education" and "cross-government action" was needed to stop the creation of a "lost generation" due to poor mental health.
Many of the findings are based on the Labour Force Survey, which has recently been stopped by the Office for National Statistics because the numbers taking part had fallen.
However, the Health Foundation has previously said it believes the data is still accurate enough for its analysis.
