Specialists from the universities of Oxford, Exeter, Manchester, Glasgow and Sheffield, and the Centre for Mental Health, are calling for all prisoners to be routinely checked for signs of traumatic brain injuries.
A comprehensive review, published in The Lancet Psychiatry, suggests that bumps to the head from falls, assaults or road accidents can lead to neural injuries which alter the brain structure, and increase the risk of violence offending.
The authors claim that up to 60 per cent of people in custody have suffered some kind of head injury in the past, ranging from mild to severe.
In contrast, around one in 200 people in the general public have been admitted to hospital for a head injury according to the charity Headway.
The experts say helping prisoners receive proper treatment could prevent future offending and called on schools, doctors and hospitals to help identify youngsters who have suffered head injuries before they commit crime.
“Addressing traumatic brain injury offers a means to not only improve the lives of those who offend, but also to reduce crime,” said lead author Professor Huw Williams, of the University of Exeter.
“A range of measures could reduce the risk of crime following traumatic brain injury.
“These could include any form of neurorehabilitation, and better links between emergency departments, community mental health services, GPs and school systems that might lead to early identification and management.”
It is thought that head injuries damage parts of the brain responsible for self-regulation, impulse control and pro-social behaviour.
Links to violence and head trauma date back to the Vietnam War, when it was noted that veterans who had suffered brain injuries to the front of their heads - an area involved in planning, decision making and emotional regulation - became far more aggressive.
Some of Britain’s most notorious criminals including Fred West and Ronnie Kray also notably suffered head injuries.
Study author Prof Seena Fazel, Professor of Forensic Psychiatry, University of Oxford, said: “It does seem to matter where the injury occurred. Frontal injuries appear to have more impact on aggression.
“One of the consequences of head injury is attention-deficit hyperactivity disorder, and studies have shown that treatment for ADHD leads to a reduction in criminality and that’s down to reduced aggression. So treating symptoms like that could help.”
The new review, based on all literature on the subject to date, found that between 10 and 20 per cent of inmates have a complicated, moderate or severe head injury, while an additional 30 to 40 per cent have a mild brain injury.
Andy Bell, Deputy Chief Executive, from the Centre for Mental Health said: “Up to 60 per cent of adult offenders are thought to have a history of head injury, often alongside numerous other traumas in their lives.
“For some people, serious and repeated head injuries, particularly early in life, have been associated with an increased risk of offending alongside a range of other difficulties in life including poor mental health.
“Identifying those who have emotional or cognitive difficulties resulting from a brain injury may help to ensure they get the right support to improve their mental health and potentially reduce their risk of later offending.”
However some experts argued that it was difficult to tease apart whether it was the trauma itself causing the criminal behaviour, or whether people who were more likely to offend because of their background, were also more likely to end up with a head injury.
Ryan Aguiar, Consultant Clinical Neuropsychologist at Ashworth Secure Hospital in Liverpool where Ian Brady was detained until his death last year, said: “Brain injury does not lead to crime even though there are more prisoners with head injury and cognitive impairment per capita or as a percentage than there is in the general population
“Crime is a much more complex condition that is brought about by a myriad of social, environmental, personality, mental health and situational circumstances.
“Head injury is only one among many and not even a first among equals.”
Graeme Fairchild, a reader in the psychology at the University of Bath, added: “One of the main problems is that many of the risk factors for criminal offending and violence, eg. being male, coming from a low socioeconomic status background, having ADHD, being physically abused, and abusing alcohol and other substances, are also risk factors for sustaining head injuries, so it is very difficult to disentangle cause and effect here.
“Many young people sustain head injuries without going on to develop criminal behaviour.”
Peter McCabe, Chief Executive of Headway – the brain injury association, whose Justice Project calls for better screening of prisoners said: “The vast majority of people who sustain a brain injury will not be involved with the criminal justice system.
“However, some of the effects of brain injury, such as memory loss, increased impulsivity, anger, and reduced inhibition can lead people into difficulty with the law and evidence suggests over representation of brain injury in offender populations.
“It is vital that we better identify brain injury at the earliest possible stage in the criminal justice system.”