The research at the Royal Marsden Hospital in London and Sutton shows that cancer patients often suffer memory flashbacks which they cannot control.

The Cancer Research Campaign says these can affect their ability to cope with the disease.

Professor Chris Brewin from the University of London studied 130 depressed and non-depressed cancer patients.

One in four patients reported distressing visual memories which intruded into their everyday life.

One in 10 of these were not depressed and one in three were depressed.

Seventy-nine per cent of the memories involved death and illness and 54% were directly related to cancer.

They included memories of incidents involving relatives who had died of cancer.

Hopeless and helpless

For the depressed patients, the post-traumatic stress disorder often coincided with the onset of their depression and worsened their anxiety.

Cancer patients suffer the same symptoms as many involved in the Hillsborough disaster

Professor Brewin said: "The flashbacks were associated with patients coping poorly with their cancer, and feeling hopeless and helpless."

Like other sufferers of post-traumatic stress disorder (PSTD) such as the Hillsborough victims, most patients tried to block out the memories.

However, they often found they could not avoid them coming back.

Professor Brewin said the patients could be helped in a similar way to people who suffer from post-traumatic stress disorder.

This would involve therapy to teach sufferers to confront their traumatic experiences in a positive way rather than blocking them out.