Young British men are much more likely to commit violent crimes if they have served in the armed forces, a study has found.
Of about 3,000 military men under the age of 30, more than a fifth had a conviction for violent offences, compared with 6.7 per cent of their civvy-street peers.
There were strong links between combat experience, post-deployment alcohol misuse, traumatic stress and violence.
Men who had seen combat in Iraq and Afghanistan were 53 per cent more likely to commit a violent offence than those with non-combat roles. Those with multiple experiences of combat had a 70-80 per cent greater risk of committing acts of violence.
In the biggest study of its kind, researchers were given access to police records on almost 14,000 randomly selected men and women who were active or former members of the armed forces, mostly the army.
Participants provided information about their experiences before and after joining the military and underwent psychological tests.
A search of the Police National Computer was made for any convictions, cautions or warnings. Overall, 17 per cent of the men had criminal records, and 11 per cent had committed violent offences. Of the 2,728 aged 30 and younger, 20.6 per cent had a criminal record for violence.
The findings, released on the tenth anniversary of the Iraq War, are published in a special issue of the Lancet medical journal.
Study leader Dr Deirdre MacManus, from King’s College London, said: “There has been a lot of media coverage and public debate about violence committed by veterans of the conflicts in Iraq and Afghanistan.
“Our study, which used official criminal records, found that violent offending was most common among young men from the lower ranks of the army and was strongly associated with a history of violent offending before joining the military.
“Serving in a combat role and traumatic experiences on deployment also increased the risk of violent behaviour.”
Violent offences covered a broad range of acts, from verbal harassment to homicide. They did not include incidents of domestic violence.
A strong association was seen between violent offending and high levels of self-reported aggression.
Professor Sir Simon Wessely, co-director of the Centre for Military Health Research at King’s College London, who co-authored the study, said: “Some people with aggressive dispositions make very good soldiers – that’s the nature of the game.
“My own view, and the view of many people in this area, is that you meet a lot of people in the armed forces who you’re glad are in the armed forces, and it’s doing them a lot of good.”
He stressed the vast majority of soldiers returning from tours of duty in combat zones never got into trouble.
“Not every single person who joins the armed forces is Sir Lancelot or Sir Galahad,” the professor said. “We are suggesting there is a problem that needs to be looked at, but just as with post traumatic stress disorder, this is not a common outcome in military populations.
“Overall, you must remember that of those who serve in combat, 94 per cent of who come back will not offend.”
He said his group had started random mental health checks on armed forces returning from active duty. This is a routine procedure in the United States.