New study could help predict suicidal behaviour in older adults

(PhysOrg.com) -- Focussing too much on the present and not using past experience to make decisions could be linked to suicide in elderly depressed adults, researchers from Cambridge and Pittsburgh have found.

Described as "myopia for the past", the findings help explain why only some older people with depression attempt suicide and could allow researchers to predict which individuals are most at risk.

Suicide rates are particularly high in older adults, but while most older adults who attempt suicide suffer from depression, the severity of depression alone does not explain suicidal behaviour.

The study by researchers at the Western Psychiatric Institute and Clinic at the University of Pittsburgh, and The MRC/Wellcome Trust Behavioural and Clinical Neuroscience Institute at the University of Cambridge involved 65 individuals aged 60 years and older.

Participants were assessed on a computerised learning task that assesses ability to use positive and negative feedback to change behaviour.

The test requires individuals to learn and relearn different rules on the basis of changes in feedback. The task is made difficult by including misleading feedback on a proportion of trials, where the participant is told that they are wrong after a correct response.

The results showed that patients who had attempted suicide were able to learn the initial rule on the task, but had great difficulty in re-learning ('reversing') when the rule changed. More specifically, they tended to continue to follow the old rule despite negative feedback for the wrong answers, and focused excessively on the last trial, ignoring past experience.

Patients who were depressed, but had never attempted suicide did not show the same effect and resembled healthy elderly volunteers.

Professor Barbara Sahakian of the University of Cambridge and a lead researcher on the study said: "This is an important step towards identifying a cognitive biomarker that will help us detect which elderly depressed patients are at high risk of attempting suicide.

"We hope that this research will ultimately lead to a reduction in this tragic behaviour."

The study is published today in the American Journal of Psychiatry.