We all encounter challenges and obstacles in life, such as divorce, death, illness and unemployment. But while some people are highly resilient and able to cope with these stresses, others struggle deeply, and may experience anxiety and depression as a result.
So why is it that some of us thrive in the face of life's trials, while others suffer? Neuroscientists may have found a clue to psychological vulnerability within a tiny emotion-processing center in the brain.
In a study published Wednesday in the journal Neuron, researchers from Duke University found that measuring the activity of the amygdala, an almond-shaped part of the brain that determines how we respond to threats, could predict whether individuals would react to stressful life events with anxiety or depression -- as early as four years before these reactions occur.
"Often, individuals only access treatment when depression and anxiety has become so chronic and difficult to live with that it forces them to go to a clinic," Duke postdoctoral researcher Johnna Swartz said in a statement. "With a brain marker, we could potentially guide people to seek treatment earlier on, before the disorders become so life altering and disruptive that the person can't go on."
Previous research has linked exaggerated amygdala activity with mental illnesses including depression, anxiety and post-traumatic stress disorder. Studies on individuals at risk for PTSD -- specifically, veterans returning from combat -- have suggested a correlation between abnormal activity in certain regions of the brain, including the amygdala, and the ability to handle stressful events.
However, these studies did not determine whether excessive amygdala activity was a causative factor in vulnerability to stress, or a reaction to stressful events.
"What has been unclear... is if this exaggerated amygdala activity precedes the experience of these problems and, more importantly, predicts who will develop these problems later in life," Swartz told The Huffington Post. "Unknown before our study was whether relatively greater amygdala activity predicts future risk for the experience of depression and anxiety in otherwise healthy individuals experiencing... stressors like losing a job, marital discord or having difficulty in school."
The Duke research team hypothesized that the findings on veterans who had returned from combat could be extended to less severely stressful life events, including divorce, illness or loss of a loved one.
To test this hypothesis, they scanned the brains of 753 healthy college students while they were looking at images of angry or fearful faces. Then, using fMRI technology, they measured activity in the amygdala to determine how active it was in response to the threatening stimuli.
Every three months after the fMRI measurements were taken, the participants answered questions assessing stressful life events, as well as symptoms of anxiety and depression. Of the original participants, nearly 200 went on to complete the surveys every three months for an average of two years, and some kept taking the surveys for up to four years. The remaining participants were not followed after the initial fMRI tests.
Those with more reactive amygdalae at the start of the study were found to experience more severe symptoms of anxiety and depression in response to later stressful life events. However, an overactive amygdala alone was not enough to predict anxiety and depression. These symptoms had to first be triggered by a stressful life event.
These findings suggest that identifying "biomarkers" -- measurable indications of the brain's biological state -- that may be able to predict later psychiatric conditions could be a promising line of research, opening up new possibilities for diagnosis and early intervention for patients with anxiety and depression.
"With continued research leading to the identification of additional biomarkers, including genes, our long-term goal is to inform efforts to prevent the experience of disabling levels of mental illness based on an individual's specific form of risk," Swartz said.
Check out the video below to hear the researchers discuss the study: