People who have suffered brain injuries are more likely to die earlier even if they appear to have recovered, a new study suggests.
Published in the JAMA Psychiatry journal, the research examined data on over two million people spanning more than four decades and found that people who have sustained blows in the head often suffer from impaired judgement.
This makes premature death more likely and those who have also had problems with psychiatric disorders as well are at even greater risk.
Each year, over one million people are admitted to hospitals because of brain traumas.
Researchers at the University of Oxford and the Karolinska Institute in Stockholm examined records of patients in Swedish hospitals between 1969 and 2009.
Of those who survived for more than six-months after their initial injury, four per cent died before they reached the age of 56.
This is in stark contrast to the number of people without injury, which stood at just 0.2 per cent.
Rates of suicide were found to be significantly greater in people who had sustained cranial injuries. They are also found to be more likely to suffer fatal injuries, such as being involved in car crashes.
Dr Seena Fazel, a research at Oxford, said: "There are these subgroups with really high rates, and these are potentially treatable illnesses, so this is something we can do something about."
Professor Huw Williams, co-director of the centre for clinical neuropsychology research, told the BBC said people with head injuries need to be given greater monitoring because rates of depression and anxiety are "huge".
A recent study carried out by the Mayo Clinic in the US found that people who have suffered brain traumas are more likely to develop Alzheimer's disease in later life.
The team believes blows to the head cause increased build-ups of amyloid plaques, the protein which is the main cause of the condition.
Other studies have suggested that high impact sports such as rugby and boxing heighten the chances of person being diagnosed with a cognitive illness.