Young British servicemen - past and present - are three times more likely to commit violent crime than their civilian counterparts.
Using official criminal records, researchers have found that violent offending is particularly common among men under 30-years-old from the lower ranks of the Army.
Of nearly 3,000 men under 30 who have served in the armed forces, nearly 20.6% have a conviction for violence, according to the study published in The Lancet today.
That compares to 6.7% of the same age group in the civilian world.
The report also shows that men who have served in Iraq or Afghanistan are 53% more likely to commit a violent offence than their colleagues in non-combat roles.
"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% of those who come back will not offend," said report co-author Sir Simon Wessely from King's College, London.
According to the figures, those with multiple experiences of combat have a 70% to 80% greater risk of committing acts of violence.
The report acknowledges that those who choose to become a soldier are likely to have a more aggressive disposition than the average person.
Pre-military history of violence, younger age, and lower rank appear to be the strongest risk factors for violent offending.
But alcohol misuse and post-traumatic stress disorder on return from deployment were also found to be strong predictors of violence.
Former Royal Engineer Lewis Mackay returned from Afghanistan in 2010 - he saw his commander lose both legs on the battlefield after stepping on an Improvised Explosive Device (IED).
He said: "When I came back I got very angry and felt very angry towards my wife.
"In my head she didn't exist whatsoever. If she did something that I didn't think was right I'd feel the urge to lash out and it got to the point where I had to physically sit on my hands to stop myself doing that."
Mr Mackay has now received the help he needed but former SAS serviceman Bob Craft says it's never easy to ask for help.
"The older you are, the better you deal with it. I asked for help and I found help.
"But younger lads who come out refuse to ask for help because it's seen as a weakness, therefore they bottle it up and then they make mistakes," he said.
The study is the biggest of its kind and is released just days before the 10th anniversary of the start of the Iraq War.
In a statement the Ministry of Defence said: "We are committed to supporting members of our Armed Forces and their families as they return to civilian life post deployment.
"That is why we funded this research and have comprehensive mental health support available before, during and after operations. We also ensure that all personnel go through a thorough period of decompression to help make this adjustment.
"Any violent offence is unacceptable and will not be tolerated by our Armed Forces. If a member of our Armed Forces or their family experiences violence there is a wide range of support and help available to them."