Inability of a brain region to adjust to stress may bring about depression
Major depressive disorder (MDD), often known as clinical depression, is among the most frequent mental health conditions in America. In line with the National Institute of Mental Health (NIMH), approximately 7.1% of adults had a depressive episode in 2017.
Furthermore, recent researchTrusted Source completed by the Centers for Disease Control and Prevention (CDC) suggests the stress of the existing COVID-19 pandemic could be associated with a rise in self-reported depression and anxiety symptoms, particularly in adults under 30 years old.
Experiencing stress over a prolonged period, such as through the pandemic, is linked to the development of depression. Among the major symptoms of depression includes anhedonia, or the shortcoming to anticipate or feel pleasure.
However, researchers do not have a comprehensive knowledge of how chronic stress brings about depression or the accompanying symptoms of anhedonia.
Evidence suggests that the medial prefrontal cortex (mPFC), a brain region involved with processing reward and regulating the stress response, may be involved in mediating these ramifications of chronic stress.
As the mPFC is involved with regulating the stress response, acute and chronic stress also elicit changes in the mPFC.
Studies in rodents have displayed that glutamate, an excitatory neurotransmitter, is released by neurons in the mPFC during acute stress.
However, rodents subjected to chronic stress exhibit lower degrees of glutamate release in the mPFC when confronted with a fresh acute stressful event.
Scientists feel that such a decrease in the mPFC glutamate response because of chronic stress is actually a protective adaptation to stress.
StudiesTrusted Source had already proven that mPFC glutamate activity is altered in depression.
Now, a report led by a team of researchers at Emory University in the usa shows that persons with depression, unlike individuals without the condition, cannot produce an adaptive reduction in mPFC glutamate levels in response to experiencing a recently available upsurge in everyday stress.
Furthermore, the extent to which a person with depression lacked this adaptive response predicted their degrees of anhedonia in daily life.
“We could actually show what sort of neural response to stress is meaningfully related to what people experience in their daily lives,” says Dr. Jessica Cooper, the study’s first author. “We now have a big, rich data set that provides us a tangible result in build upon as we further investigate how stress plays a part in depression.”
The analysis appears in the journal NatureTrusted Source.
Adaptive changes in glutamate release
To research the role of the mPFC in depression, the researchers recruited 65 individuals without depression and 23 people with MDD who were not taking medication.
Prior to the experiment, the researchers used the Perceived Stress Scale (PSS) to measure each participant’s subjective or perceived stress levels in the last month.
On the test day, the participants completed an activity that induced acute stress. The researchers used magnetic resonance spectroscopy (MRS), a noninvasive imaging technique, to measure changes in glutamate levels in the mPFC before and following the acute stress test.
The team found that the magnitude of change in mPFC glutamate levels due to the acute stress test was associated with perceived stress levels in people without depression.
People without depression and with lower degrees of recent perceived stress, as measured by the PSS, showed a rise in mPFC glutamate levels after the test. On the other hand, those without depression but with higher perceived stress showed no change or a decrease in mPFC levels.
While there have been changes in mPFC glutamate levels in people with depression through the acute stress test, these changes weren't correlated with their PSS score.
The authors recommend that the absence of an adaptive change in mPFC glutamate levels may play a role in the development of stress-related mental health issues, such as depression.
Source: www.medicalnewstoday.com
