Neuroscience Breakthroughs Since Graduate School - Part 6: Stress

Recent studies have challenged core stress concepts taught in graduate classes. We cannot turn off our physiological reactions to stressors like a light switch. Furthermore, we shouldn't attempt to do so, as arousal can improve our performance. Kelly McGonigal compellingly presents evidence that major life changes will not shorten life expectancy if we reinterpret our activation as bravely facing challenges. In addition, our prosocial actions can protect us from the harmful effects of major life changes. Dr. Inna Khazan persuasively argues that a mindfulness approach to stress can enhance our cardiovascular and neuroendocrine responses to stressors.

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Challenges to Homeostasis

Claude Bernard, Walter Cannon, and Hans Selye were influential scientists who contributed significantly to the development and understanding of the concept of homeostasis, which refers to the ability of living organisms to maintain internal stability and balance in the face of changing external conditions.

Claude Bernard (1813-1878) was one of the first scientists to recognize the importance of maintaining a stable internal environment for the proper functioning of the body's cells and organs. He introduced the concept of the "milieu intérieur" (internal environment) and argued that the role of physiological processes is to maintain a constant internal environment, which is necessary for life. Bernard's work laid the foundation for the concept of homeostasis and emphasized the importance of the body's ability to regulate its internal conditions.

Walter Bradford Cannon (1871-1945) built upon Bernard's work and coined the term homeostasis to describe the dynamic equilibrium that living organisms maintain to ensure their survival. He identified several key physiological mechanisms responsible for maintaining homeostasis, such as the regulation of body temperature, blood sugar levels, and pH. Cannon also introduced the "fight or flight" response, which refers to the body's acute stress response and the physiological changes that occur to prepare an organism for action in the face of a threat.

János Hugo Bruno "Hans" Selye (1907-1982) is best known for his research on stress and its effects on the body. He developed the concept of the "general adaptation syndrome" (GAS), which describes the body's three-stage response to stress: alarm, resistance, and exhaustion. Selye's work contributed to our understanding of how the body strives to maintain homeostasis in the face of stressors and how chronic stress can lead to maladaptive responses, negatively affecting overall health.

Together, the work of Claude Bernard, Walter Cannon, and Hans Selye has helped shape our understanding of homeostasis as a fundamental principle governing the function of living organisms. Their research has provided valuable insights into the complex regulatory systems that enable organisms to adapt and respond to their environments, ensuring their survival and well-being.

We will discuss powerful challenges to homeostasis, including cataclysmic events, early life stress/adversity, and childhood trauma.

Cataclysmic Events

Lazarus and Cohen (1977) described cataclysmic events as "sudden, unique, and powerful single life-events requiring major adaptive responses from population groups sharing the experience” (p. 91).

Intentional and unintentional, these events can impact local communities (e.g., mass shootings), geographic regions (e.g., earthquakes, fires, hurricanes, and tsunamis), and the entire planet (e.g., the COVID-19 pandemic. These catastrophes can produce death, dislocation, fear, grief, trauma, and Post-Traumatic Stress Disorder. Graphic © Syda Productions/Shutterstock.com.

Many factors influence survivor response to these powerful stressful events, including perceived discrimination, resources, support, vulnerability to future harm, distance from the devastation, and media coverage. The stressfulness of an event is influenced by geographic proximity, its recency, and whether it was intended. Intentional events are more traumatic than natural disasters because the perpetrators targeted the victims and could do so again (Brannon et al., 2022).

Traumatic Stress and Post-Traumatic Stress Disorder (PTSD)

Traumatic stress is produced by a highly intense stressor that disrupts coping and endangers ourselves or others. Post-Traumatic Stress Disorder (PTSD) is a severe and long-lasting trauma and stressor-related disorder that often develops within three months of a traumatic event. DSM-5 (APA, 2013) divides its symptoms into four clusters: intrusion, avoidance, negative alterations in cognition and mood, and alterations in arousal and reactivity. Graphic © John Gomez/Shutterstock.com.

The exposure can also be second-hand, such as witnessing domestic violence or learning about a family tragedy (Crider, 2004; Lamprecht & Sack, 2002). The lifetime prevalence of adult PTSD in the United States is about 6.8% (Kessler et al., 2005).

While the earliest model of PTSD focused on trauma during combat, subsequent research has shown that crime, domestic violence, natural disasters, sexual assault, and terrorism can precipitate PTSD symptoms. Since women are more likely than men to experience these stressful events, it should not be surprising that they are more often diagnosed with this disorder (Stein et al., 2000). Children and adolescent victims and witnesses of violence also share an elevated risk of PTSD (Silva et al., 2000).

A single traumatic event can reshape synapses and increase electrical activity in the amygdala 10 days later. The N-methyl-D-aspartate receptor (NMDA-R) protein, which plays a central role in long-term memory, mediates these changes (Yasmin et al., 2016). Amygdala graphic © Kateryna Kon/ Shutterstock.com.

Early Life Stress/Adversity (ELA)

Birnie and colleagues (2023) reported that early-life stress could disrupt reward circuitry, resulting in anhedonia or loss of pleasure and motivation. They discovered a corticotropin-releasing hormone (CRH)/gamma-aminobutyric acid (GABA) pathway from the basolateral amygdala to the nucleus accumbens in mice. Adverse experiences overactivated this pathway, disrupting reward-seeking behaviors. Silencing this pathway restored reward behaviors.