For patients with depression, there isn’t much hard science to help you or your doctor decide your best course of treatment – if talk therapy is right for you, or if you need antidepressants, such as Prozac. The wrong choice can bring on months of added suffering. But now a new study involving brain scans could change that.

Published in journal JAMA Psychiatry, the study involved 65 people with depression who had been randomly assigned to receive either 12 weeks of treatment with the antidepressant escitalopram oxalate (Lexapro), or cognitive behavioral therapy (CBT), the most scientifically studied form of talk therapy for depression. CBT works by helping patients reframe negative thoughts and perceptions to help alter their mood.

Researchers from Emory University in the US took PET scans of the patients’ brains both before and after their treatments, and then compared the brain activity of people who responded strongly to their treatment -- enough to resolve their depression -- to those of patients who didn’t respond at all. Partial responders were not included.

Patients who responded well differed from those who didn’t in one particular way -- in the activity of the insula, a brain region that assesses signals related to pain, temperature, and heart rate. While the insula tends to be active when sad, disgusted, or afraid, it also plays a role in pleasure.

“Low activity in the insula at baseline may reflect impaired sensitivity to signals [of] one’s internal state,” said lead author Dr. Helen Mayberg.

Findings showed that people who had less activity in the anterior part of the insula had better odds of success with CBT, but lower odds with medication. Yet for people with higher baseline activity in the insula, the situation was reversed: they responded to the medication and not as well to CBT.

While more research needs to be done, the study does illuminate how some brains work differently, and that this affects how they respond to treatments. Forbes magazine writes that "this is particularly relevant since, as the authors point out, when a medication doesn’t work for a patient, he or she is often put on another one, rather than being switched to psychotherapy."

Access the study: http://www.ncbi.nlm.nih.gov/pubmed/23760393