Brain Scans Could Change How We Diagnose Depression

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The difficult cases

About 30 percent of patients don’t respond to medication or therapy and are considered to have “treatment resistant” depression.

They may go into the hospital for more intensive care, and if needed, also undergo electroconvulsive therapy (ECT), which involves controlled electric currents sent through your brain while you are under general anesthesia.

Although this is the most reliable choice for these patients, about half of them relapse after a year on medication. The procedure may cause memory loss.

Another option is transcranial magnetic stimulation (TMS). This involves a large electromagnetic coil placed on the forehead and short pulses directed into the brain (there is some choice about where).

Patients often prefer TMS because it has fewer risks, but current research suggests only a rough guideline about who might benefit. That includes someone who has been depressed no more than three years and does not have psychosis.

It takes up to five weeks to know if you’ve responded, and less than 40 percent do, according to various assessments.

Liston’s team studied patients who had a brain scan shortly before a five-week course of TMS on the dorsomedial prefrontal cortex. If those patients also fell into one of the subtypes involving anxiety, 82 percent improved significantly, compared to 61 percent in another subtype, and less than a third in the other two.

It turned out that the brain scan information was more predictive than any symptom. That’s a big step toward “potentially precision medicine in psychiatry” Liston said, a biomarker with “87 to 94 percent accuracy” of who would respond to this type of TMS.

Deep-brain stimulation (DBS), another option, is still in the experimental stage for depression — where to apply the stimulation is an open question.

This therapy was first developed to reduce tremors from Parkinson’s disease. The targeting for that purpose is still being fine-tuned. With this technique, two electrodes are surgically put directly in the brain.

Among 77 patients who received stimulation in an area called the subcallosal cingulate at eight centers around the country, around half responded, and a bit less than a third were no longer considered depressed after a year.

A group at Emory analyzed the brain scans of those that responded, and used those results to refine the stimulation targets. When they tried this out in 11 patients, 9 responded and 6 were in remission after a year.

Another frontier involves teasing out which patients who are depressed actually have bi-polar disorder. These patients, who get worse on standard antidepressants, typically try that medication first.

Liston and others are working on that issue and he hopes for results in a year.

As of today, more research is needed to make brain imaging a useful tool to diagnose and treat depression.

The field is overdue for new treatments. If brain scan research clarifies the underlying biology, that could change, Liston noted, and we could “develop fundamentally new drug and other interventions that aren’t just kind of cousins to the drugs that we have today.”

One day, biomarkers could even help us identify people at risk early and prevent major episodes.

“Just like you can test for a blocked artery, we might have a psychological stress test,” Mayberg said.

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