A new PET tracer can determine ahead of time whether a drug can successfully treat major depressive disorder (MDD), according to a study published in the April issue of The Journal of Nuclear Medicine.

“In this study we use a PET tracer that targets the serotonin transporter, an important protein within the serotonergic system,” Dr. Mala R. Ananth of Stony Brook University in New York, told HCB News. “Dysfunction of the serotonergic system is a common hypothesis for the underlying cause of MDD.”

In clinical psychiatry, there are currently no objective markers to predict if a treatment will be effective. 11C-DASB PET imaging could change that.

The drug escitalopram, which is a selective serotonin reuptake inhibitor (SSRI), has been shown to be an effective treatment for MDD, but it doesn’t work for every patient. A 11C-DASB PET scan can determine which patients will benefit by measuring the level of serotonin transporter protein present before treatment.

Ananth and her team had 31 healthy participants and 26 untreated patients with MDD receive a 11C-DASB PET scan. The MDD patients then underwent eight weeks of standardized therapy with escitalopram.

They found that patients who responded well to the treatment had less serotonin transporter proteins before treatment began. This suggests that pre-treatment neurobiology could be used to predict treatment response.

“Here we find that patients with MDD who achieve remission following treatment with a specific SSRI (escitalopram) exhibit differences in the serotonin transporter in a region important for emotional processing prior to treatment,” said Ananth.

She added that these findings may be applicable for any disorder in which SSRIs are used, including obsessive-compulsive disorder, but that further research is needed to confirm that.