Chronic Stress and Brain Health
Long-term exposure to stress, known as chronic stress, causes maladaptive responses such as anxiety, depression, cognitive dysfunction, and anhedonia, which is the inability to experience pleasure.
In the study of stress, the amygdala has received the most attention. The amygdala senses threats like a smoke detector recognizes smoke. It is the alarm that initiates the fight-or-flight stress response when we face threats to our health and relationships, or from our work and other endeavors we care deeply about.
When the amygdala senses a threat, it activates the HPA Axis, which is the fight-or-flight signaling system made up of the Hypothalamus to Pituitary to Adrenal glands. The HPA Axis launches a surge of stress hormones which increase blood sugar, heart rate, and blood pressure to provide the energy boost necessary to respond to the challenge. These are adaptive responses that help us cope with short-term challenges, meant to be temporarily deployed.
New research provides more information on the activation of the hypothalamus, but also its role in recovery from chronic stress. The hypothalamus has two kinds of brain cells that interact with the same receptors, and act as a counterbalance to each other:
· proopiomelanocortin (POMC) neurons, which are activated by stress; and
· agouti-related protein (AgRP) neurons, which inhibit the stress response.
Increased activation of the POMC neurons for 3 days did not result in maladaptive responses, but activation for 10 days did result in depression and anhedonia. POMC neurons fired more regularly after exposure to chronic stress. Repeated firing of POMC brain cells causes dysfunction of this system and is likely crucial in the development of mental health problems caused by exposure to chronic stress.
Activation of AgRP neurons reverses the mental health issues caused by chronic stress. Because AgRP brain cells can release GABA, a transmitter known to increase calm, researchers believe GABA is at least partially responsible for decreasing the activation of POMC neurons.
Takeaway: Changes in the brain result in fluctuations in our mental health. Exposure to 10 days of stress causes repeated firing of brain cells in the hypothalamus, and heightened risk of mental health problems. The good news is that activation of POMC neurons is reversable.
Individuals: Monitor your exposure to stress, and make an effort to limit stress and maximize resilience.
Leaders: Work and education cultures can be chronically stressful. Recovery is possible with a reduction in stress. Leaders of stress-prone cultures should strive to understand:
· the role the environment has in creating chronic stress in people;
· the negative impacts that chronic stress has on mental health and cognitive function; and
· the ways in which they can reduce chronic stress in their environments.
Well-being is a journey, not a quick fix
Sources
Medina, J., Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School 62-67, (2009).
Fang, Z, et al., Increased intrinsic and synaptic excitability of hypothalamic POMC neurons underlies chronic stress-induced behavioral deficits, Molecular Psychiatry, Dec. 6, 2022, Increased intrinsic and synaptic excitability of hypothalamic POMC neurons underlies chronic stress-induced behavioral deficits | Molecular Psychiatry (nature.com)
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