A new study led by Stanford Medicine has been published JAMA Network1 suggests that a particular “cognitive biotype” of depression may respond poorly to standard antidepressants.

Hold: What is a biotype? According to the American Psychological Association, biotype refers to a group of individuals with a similar genetic makeup. In this case, biotype refers to people who share similar neural structures when it comes to learning and processing information and regulating mood.

The study focused on those with a cognitive biotype that made it harder for them to plan ahead, stay focused, and exercise self-control (as shown by brain imaging scans that measure activity in specific brain regions). Typical symptoms of depression, including problems with executive functioning, decision-making, memory, concentration, and the ability to suppress negative emotions in favor of positive behavior, are more pronounced in this cognitive biotype.

In the study, researchers took 1,008 treatment-naïve adults with major depressive disorder and randomly assigned each person to one of three common antidepressants: escitalopram (also known as Lexapro), sertraline (Zoloft), and venlafaxine-XR (Effexor). A total of 712 participants completed the eight-week regimen.

Both before and after treatment with antidepressants, participants’ depressive symptoms were assessed using two surveys (one administered by a clinician and the other self-reported) and a cognitive assessment.

During this assessment, participants completed a series of cognitive tasks to measure things like memory, decision-making speed, and attention span, while fMRI monitored the activity of their neurons.