Injuries to the head can pose major risks to victims even years later as a result of impaired judgement, according to a new study.

The research collected 40 years of data on over two million people and found that having had a brain injury in the past trebled your risk of death at a later stage.

It was found that suicide and fatal injuries were among the commonest causes of later deaths.

Those with a history of mental health problems before the injury were most at risk of dying prematurely, it was found.

The study found that where there was no previous brain injury, only 0.2% of people were dying before the age of 56.

However, the death rate before this age was three times higher in patients who had previously suffered serious brain injury.

Common causes of premature death among those who had a previous brain injury included suicide, assault or suffering injuries in accidents such as car crashes. Such deaths were linked to impaired judgement as a result of the original brain injury.

The study was carried out by researchers at the University of Oxford and the Karolinska Institute in Stockholm, and looked at Swedish medical records from 1969 and 2009.

The study is published in the journal JAMA Psychiatry.