Stress In The Modern World
In today’s world, stress has become an area of keen interest not only to researchers and neuropsychologists, but to society in general. With the increase in dual income families, access to work and family on the same device, and constant updates from one’s favorite sports team or social media, it now seems that individuals scarcely get a chance to recover from one stressor before the next appears. Recently, Dr. Robert Moss and I were invited to contribute a chapter on the cognitive aspects of stress in an upcoming textbook, Stress in the modern world: Understanding science and society (edited by Dr. Serena Wadhwa). In this chapter we explore proven and familiar aspects of stress, such as cortisol, and hypo-pituitary-adrenal influences on stress, in relation to newer findings. We also discuss recent research linking prolonged cortisol levels to depression, and consider how the clinical biopsychosocial model explains the effects of stress on neurological functioning.
In the first section of the chapter, we describe the different areas of the brain that are affected by stress. Of these, the major regions are: the prefrontal cortex, amygdala and hippocampus, the hypothalamic-pituitary-adrenal (HPA) axis, and the sympathetic-adrenal-medullary (SAM) system. In addition, we note that two major factors related to stress involve the release of the neurotransmitter norepinephrine and the neuromodulating hormone cortisol; and that the research indicates a role for each of these substances in the cognitive sequelae of stress. Upon release, the hormones produce a normal, protective response to stress; however, prolonged exposure to these hormones conditions the brain to the stress response through repeated exposure, triggering anxiety, panic attacks, post-traumatic stress, and other anxiety disorders. We note also that—based upon the described mechanisms—some neurons may become overexcited and eventually stop functioning in the manner they are supposed to, potentially resulting in neuronal atrophy. Finally, we discuss the long-term effects of cortisol, which can cause the brain to age more rapidly: the result is stroke, Alzheimer’s, and dementia.
The effects of cortisol and related neurotransmitter changes, which are associated with the most common mental health disorders in the United States—such as anxiety disorders (18.1%), mood disorders (8.1%), and depression (7%)—are also discussed. All of these disorders have strong relationships to cortisol and stress exposure, as is clear from the new research we describe, which suggests one of the primary biological indicators of depression is elevated cortisol levels in the blood. It has in fact been proposed that serotonin, generally associated with depression, is not the cause of depression; but, rather, that neurochemical and anatomical changes related to the stress response are the cause.
There are some stark contrasts between the long- and short-term effects of stress on the brain, which need to be clearly differentiated. Memory consolidation during acute periods of stress is a short-term effect that may improve due to higher cortisol levels; working memory and learning have also been shown to amplify in the prefrontal cortex due to heightened cortisol levels. However, the negative aspects of short-term stress include impaired memory and cognitive functioning (i.e., working memory, memory recall, and the ability to regulate behavior, thoughts, and emotions). In addition, areas of the brain that respond to stress may impair performance involving other executive functions, such as cognitive flexibility, working memory, and set-shifting—all as described in detail in the chapter.
Despite the obvious short-term effects of stress on cognition, we have identified long-term effects that cause impairments and are less reversible. For example, it has been found that short-term and working memory impairment are positively correlated with heightened cortisol activity and stress in childhood, regardless of the cause (e.g., poverty or abuse). These early life stressors stymie the development of brain regions associated with executive and affective functioning, and higher order cognitive capabilities.
The chapter also integrates a new theoretical view based on Dr. Moss’s clinical biopsychological model, which is based on the cortical column (i.e., macrocolumn) as the binary unit (or bit) involved in learning and memory. The model describes predictable patterns in the types and manner of processing in various cortical regions, and explores how processing in one region may interact with other regions, both intrahemispherically and interhemispherically. We briefly discuss how the proposed model illustrates how stress leads to enhanced initial memory storage, impaired information retrieval and working memory, and subsequent deficits in attentional set-shifting and cognitive flexibility. In relation to enhanced memory consolidation, the theory explains that the basis for learning and memory involved with higher cortical functions relies on information stored in columnar circuits.
The authors encourage the reader to consider in particular that each cortical column is a group of a few thousand neurons that represents a specific information bit. With the increased arousal, columnar circuit activation increases, and this, in turn, is theorized to lead to enhanced memory. Internal and self-referential processing involves the medial areas of the cortices while external or environmental processing involves the lateral cortices. The medial cortical areas receive input from and provide input to subcortical structures. The higher the stress load—especially when including self-referential aspects—the more likely it is that the medial regions will be activated and thus interfere with activities in the lateral cortex. No matter whether the right hemisphere’s excitatory receptive sensory processing is the result of new internal stressors, or external stressors, activation of the right frontal lobe and its inhibitory influence on the left frontal lobe occurs regardless, resulting in impaired retrieval of left hemisphere verbal information and set-shifting.
Overall, we hope to provide students with a basic understanding of the cognitive effects of stress—to understand that these can be debilitating at times, as well as contribute to various mental health disorders. It is hoped that the research we discuss, and the information we provide, will prove helpful to students in clarifying the cognitive neuroscience of stress.
Stermensky II, G., & Moss, R. A. (in press). Chapter 14: Cognitive symptoms and effects of stress. In Wadhwa, S (Ed.), Stress in the modern world: Understanding science and society. Santa Barbara, CA: ABC-CLIO.
Gage Stermensky II is a doctorate student in clinical psychology at Forest Institute, Associate Faculty at the University of Phoenix (Chicago) in social sciences and research, and a Psychology Fellow at the Gateway Foundation in Lake Villa, Illinois.