One in 13 young people in England and Wales experiences post-traumatic stress disorder by the age of 18, the first research of its kind suggests.
A study of more than 2,000 18-year-olds found nearly a third had experienced trauma in childhood. And a quarter of these then developed PTSD, which can cause insomnia, flashbacks and feelings of isolation.
Researchers say, with many young people not receiving the support they need, the study should be a "wake-up call".
The study, found slightly more than half of those who had had PTSD - an anxiety disorder caused by very stressful, frightening or distressing events - had also experienced a major depressive episode and one in five had attempted suicide.
But only the same proportion - one in five - had been seen by a mental health professional in the past year.
Lead researcher Dr Stephanie Lewis, a Medical Research Council-funded researcher at the King's College London Institute of Psychiatry, Psychology and Neuroscience, said: "Providing effective treatments early on could prevent mental health problems continuing into adulthood."
