Stanford Medicine has identified an fMRI metric that could indicate the likelihood of relieving depression with medication, according to a study published in the Proceedings of the National Academy of Sciences in the United States of America.
If you’ve ever impulsively responded in a fierce manner to a friend or family member and regretted it, you might’ve experienced an “amygdala hijack.” In a stressful situation, the amygdala may perceive a threat and react milliseconds earlier than the neocortex, or so-called thinking brain.
The amygdalae are two small glands deep within the brain that have an outsize role in emotional processing and memory—sometimes leading to a fight-or-flight response. Over-reactivity of the amygdalae and early life stress (ELS) have been strongly implicated in the neurobiology of depression, but they’ve never been investigated together, according to researchers from Stanford Medicine’s Department of Psychiatry and Behavioral Sciences.
To induce amygdala activity, they showed subjects pictures of people with happy or sad facial expressions and measured the subjects’ reaction on functional MRI.
Researchers found that in depressed subjects with a history of ELS, the likelihood of remission with antidepressants is highest with greater amygdala reactivity to happy faces. Conversely, for those with a low amount of ELS, remission is associated with lower reactivity to all stimuli.
“The present findings advance our current knowledge by demonstrating that information on amygdala function and interactions with exposure to ELS together may be used to form the most accurate predictive model for antidepressant remission,” wrote the authors.
ELS can cause individuals to develop a high sensitivity to facial cues, presumably to avoid a confrontation with a caregiver. This defense mechanism can change the functional structure of the brain, manifesting later in life as increased sensitivity to negative signals. However, individuals who exhibit this reactivity to both positive and negative stimuli stand a better chance of successful treatment.
A mass-market exam testing the viability of antidepressants using happy or sad faces is still a while off, but the ELS/amygdala reactivity metric could be useful moving forward.
“Such a metric also offers a viable target for future mechanistic investigations and for studies aimed at developing novel interventions. Moreover, these findings provide additional support for the need to consider a life-course approach to the prevention and treatment of mental disorder,” the authors wrote. “Metrics based on combined brain and life experience data hold promise for developing a neuroscience-informed approach to mental disorder and its management.”