Nature Middle East | House of Wisdom

Researchers can now tell who will be depressed, or not, in response to stressors

Two people, with similar circumstances, can experience the same stressor – death, trauma or even bankruptcy – and one could go on to develop depression while the other would weather the crisis and come out unharmed. What makes the difference between one and the other? Why do some function normally following a crisis, or are more resilient, while others become emotionally crippled by it?

Scientists from Duke University, Durham, believe they have a clue in the form of an almond-shaped group of nuclei in the temporal lobe of the brain called the amygdala whose reactivity during such circumstances can indicate future vulnerability to depression or anxiety – essentially acting as a predicative marker of risk.

It’s not the first study that attempts to link individual differences in brain activity to the ability to handle trauma and stress; activity of this area is crucial for detecting and responding to danger.

Previous studies, however, looked at participants who endured highly traumatic events, like war and active combat, but this study focuses on the general population, who encounter less punishing forms of stress, like divorce, or loss of a loved one.

A longitudinal study of 340 healthy young adults published this February in Neuron, and flagged in Duke Today, the university’s e-publication, explores how experiencing stressors increases the likelihood of developing treatment-resistant, chronic psychological problems, including depression and anxiety, for some, but not others.

The scientists measured the intensity of this activation using functional magnetic resonance imaging.

The research, done in the lab of senior author Ahmad Hariri, professor of psychology and neuroscience, concludes that amygdala reactivity interacts with stress to predict internalizing symptoms, occurring as much as 1 to 4 years after scanning. The study also traces individual differences in how the brain reacts. “These results highlight a readily assayed biomarker, threat-related amygdala reactivity, which predicts psychological vulnerability to commonly experienced stressors and represents a discrete target for intervention and prevention,” reads the paper.

Depression, globally, is responsible for more “years lost” to disability than any other conditions, revealed Nature magazine in a special portfolio on depression. Some 350 million suffer from it, according to the WHO, and it remains widely undiagnosed and untreated in many places because of stigma, or underreported or misdiagnosed in others. In November 2014, Nature tracked prevalence of depression across countries, and many Arab countries came on top of those highly affected by the mental condition. In fact, of the first 20 countries with highest prevalence of depression worldwide, 12 of those were Arab.

“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,” explains the study’s first author Johnna Swartz, a Duke postdoctoral researcher, in Duke Today. “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.”

Hariri and his team say they will continue to follow up with, and monitor, their study participants – with the ultimate goal of understanding why some are more susceptible to mental health problems, as per a long-term project launched by Duke Neurogenetics Study.

“We [also] want to know just how far in the future knowing something about an individual’s brain helps us understand their risk,” says Hariri.

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