A new study identifies a novel biomarker indicating resilience to chronic stress. This biomarker is largely absent in people suffering from major depressive disorder, and this absence is further associated with pessimism in daily life, the study finds. Researchers used brain imaging to identify differences in the neurotransmitter glutamate within the medial prefrontal cortex before and after study participants underwent stressful tasks. They then followed the participants for four weeks, using a survey protocol to regularly assess how participants rated their expected and experienced outcomes for daily activities. “In many ways, depression is a stress-linked disorder.” “To our knowledge, this is the first work to show that glutamate in the human medial prefrontal cortex shows an adaptive habituation to a new stressful experience if someone has recently experienced a lot of stress,” says senior author Michael Treadway, professor in Emory University’s department of psychology and department of psychiatry and behavioral science.