Depressed Elderly Adults Who Attempt Suicide Ignore Previous Experience, Dombrovski-Led Study Finds

Being too focused on the present and not factoring past experiences into decisions could contribute to suicide attempts in elderly depressed adults, according to a study by University of Pittsburgh School of Medicine and University of Cambridge researchers. Using a computerized test of the ability to change behavior based on positive and negative feedback, researchers found that those who have attempted suicide performed poorly.

“This is an important step forward in understanding why some people with depression take their own lives while others do not,” said Alexandre Y. Dombrovski, the study’s lead author and an assistant professor of psychiatry in Pitt’s Department of Psychiatry. The study was published March 15 in the American Journal of Psychiatry.

Suicidal acts are most commonly linked to depression. While two-thirds of older adults who attempt suicide suffer from depression, the severity of the depression alone does not explain suicidal behavior. Identifying factors that are specific to suicidal behavior could help predict which individuals with depression are most at risk.

The researchers assessed 65 individuals, ages 60 and older, using a computerized test that required the individuals to make the best possible choices in an uncertain and changing environment. The task was made difficult by including occasional misleading feedback, where the participants were told that their answers were wrong after a correct response, and by changing the rules midway through the task. The study included participants who had attempted suicide, were depressed and had contemplated suicide but hadn’t attempted it, were depressed but not suicidal, and were neither depressed nor suicidal.

The researchers found that most of the participants who had attempted suicide were able to learn the initial choice rule on the task but had greater difficulty relearning it when the rule changed;  they also were more sensitive to the misleading feedback. A smaller subset of that group tended to continue following the old rule despite negative feedback for wrong answers. By building a machine-learning algorithm that matched the behavior of every participant, the researchers discovered that participants who had attempted suicide focused excessively on the last trial, ignoring prior experiences. Participants who were depressed but who had never attempted suicide did not show the same problem and more closely resembled healthy elderly volunteers.

“We consider this an important advance in understanding the decision processes in those elderly depressed patients who may be at high risk of attempting suicide,” Dombrovski said. “Older adults vulnerable to suicide seem to make overly present-focused decisions, ignoring past experiences. This may explain why people in a suicidal crisis fail to consider important deterrents and see suicide as the only solution. We are now using brain imaging to look at brain activity in suicidal older adults as they make decisions. We hope that this research will help doctors develop talk therapies, medications, and brain stimulation treatments for suicidal, depressed older people.”

The study was supported in part by funding provided by the National Institute of Mental Health, the American Foundation for Suicide Prevention, and the John A. Hartford Foundation.