One in 13 under 18 year-olds has been found to have post-traumatic stress disorder (PTSD) in a new study, published in The Lancet Psychiatry.

Researchers found that 642 out of 2,064 - nearly a third - of participants reported trauma exposure at a young age, with 160 of 2063 of them experiencing PTSD by the age of 18 years.

Despite this, only one in five had been seen by a medical professional over the last year.

Further to this, trauma-exposed young people were twice as likely as non-traumatised participants to develop a wide range of mental health conditions, with half of young people with PTSD having self-harmed, one in five had attempted suicide since the age of 12 years, one in four were not in education, employment, or training, and half experienced high social isolation or loneliness.

The study also reported that PTSD was not the most common mental health condition in trauma-exposed young people, as those with higher base rates, such as depression, conduct disorder, and alcohol dependence, were also the most prevalent.

PTSD is an anxiety disorder caused by very stressful, frightening or distressing events commonly associated with the military, making it a common misconception that the disorder is limited to military personnel.

Senior researcher Professor Andrea Danese, from the King's College London Institute of Psychiatry, Psychology and Neuroscience, told the BBC: "Our findings should serve as a wake-up call. Childhood trauma is a public-health concern - yet trauma-related disorders often go unnoticed. Young people with PTSD are falling through the gaps in care and there is a pressing need for better access to mental health services."