Pupil dilation may link to depression

The saying, “eyes are the windows to the soul” may be more than just a proverb.

According to one Penn researcher, pupillometry — the measurement of the pupil’s width — may be able to help clinicians figure out the right treatment method for patients who struggle with depression.

Researchers from the University of Pittsburgh, along with Michael Thase — a professor of psychiatry at Penn’s School of Medicine — have recently published a study in Biological Psychiatry which suggests that measuring pupil dilation can help predict whether a patient will respond to cognitive therapy.

As it stands right now, cognitive therapy is only effective for 50 to 60 percent of patients, Thase said.

The study, which began at the University of Pittsburgh in 2005, had psychiatric patients repeat a certain task that “involved negative words about themselves,” Thase said. Patients who exhibited a larger and more sustained pupil dilation while performing these tasks “had more difficulty responding to [cognitive] therapy than the other patients.”

Pupil dilation in response to emotional words “reflects activity in brain regions involved in depression,” Greg Siegle, the study’s lead author, explained on ScienceDaily.com.

Thase said the study was a follow-up to an earlier one, which found that brain scans can help identify patients that respond well to cognitive therapy. The cost of such a test is too expensive to be performed regularly by psychiatric clinicians.

“Functional MRI … is an expensive test,” Thase said. “Very few people think it could ever be used as a pre-treatment identifier just because of its cost and complexity.”

Thase also said he sees potential for this pupil assessment to be used in psychiatric clinics if the findings are replicated in a future study.

“The cool thing about the pupillometry test is that the hardware … is much, much, much less expensive,” he said. “It’s not outside the realm of possibility to think that a clinic could have a set-up where testing like this could be done.”

William Alexander, director of Counseling and Psychological Services, is optimistic about what pupil assessment tests could do for the field.

As it stands now, most “professionals decide what therapy to use based on their own preferences, their own education and the presentation of the client,” Alexander said. “If there becomes a simple way to discern whether a person is more susceptible to this treatment versus that, that would be a wonderful thing, and even better if it’s the kind of test that could be administered by a clinician.”

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