Frightening and often delusional memories that follow time spent in a hospital intensive care unit can lead to post-traumatic stress disorder, but a new study shows PTSD can be prevented by keeping a diary of a patient's stay.

Patients who received diaries of their ICU experiences — which family members or hospital staff had kept for them — soon after discharge were less than half as likely to develop PTSD as those who didn't receive a diary shortly after discharge, according to an international team of researchers led by Dr. Richard Griffiths and Dr. Christina Jones of the University of Liverpool in England.

Studies have shown that about 10 percent of patients whose ICU treatment is longer than 48 hours develop PTSD, a severe anxiety disorder that can occur after any psychological trauma.

"It is likely that the fragmentary nature of their memories and the high proportion of delusional memories, such as nightmares and hallucinations, make it difficult for patients to make sense of what has happened to them," Griffiths said. "Hard evidence of what really happened, in the form of a diary filled out by the treatment staff, may help to allay these fears."

Griffiths and Jones, who have studied aspects of intensive care for more than 20 years, worked with researchers from six European countries for three years on the study. The results were published Sept. 16 in the journal Critical Care.

Griffiths told MyHealthNewsDaily that other researchers have assumed patients' PTSD was linked to unpleasant real experiences in the ICU. While this may be true for some patients, he said, this study suggests delusional experiences and lack of real memories can bring on the anxiety disorder, and it can be prevented by "building their autobiographical experience."

In the study, patients' family members and ICU staff kept diaries that featured simple information about their treatment, including photos taken at different stages of their illness. Half of the 352 patients were given the diaries shortly after discharge and the other half received them three months later, at post-ICU clinical visits.

"Delusional experiences, if not counteracted by strong, real experiences, can seem real and very vivid," Griffiths said. "They are not false as such, but rather often they involve misinterpretation of real events and sounds. Many ICU patients at some time are delirious due to illness or the drugs we use. It is those delusions, which are very frightening and appear to be life-threatening, that can cause PTSD."

Even patients who at first seem uninterested in reading their ICU diaries change their minds, Griffiths said.

"Most patients want them, and even those that say they don't often come back later," he said. The diary is carefully introduced to the patient, with a relative present. They can use it to reflect on at home or work, in their own time. Many look at it several times and show other people, he said.

The main cost of providing the diaries is the time involved on the part of the ICU staff, Griffiths said. However, "compared with providing formal therapy to all patients struggling to cope with their experiences, diaries are likely to be highly cost-effective."

 This article was provided by MyHealthNewsDaily, a sister site to LiveScience.