Childhood trauma alters genes and can be passed onto future generations, new research has found. A study examining the offspring of children displaced during the Second World War revealed they were up to four times more likely to suffer from serious mental health conditions compared to those whose parents stayed at home.

In the largest investigation ever of its kind, researchers examined the health records of 3,000 children of Finnish people evacuated to Sweden during the 1941-45 conflict with Soviet Russia.

The evacuees, many of whom were at a pre-school age, were placed with foster families in Sweden and were forced to learn Swedish, later returning to Sweden.

The study found that the children of these girls had an increased risk of being hospitalised for conditions such as depression and bipolar disorder, however this was not replicated among children of boys displaced during the war.