Psychoneuroimmunology
Psychoneuroimmunology
Psychoneuroimmunology (PNI) is the study of interactions between the mind, the nervous system, and the immune system. The mind involves thoughts, emotions, and experiences; the nervous system involves the brain, the spinal cord, and nerves; and the immune system involves cells and organs protecting the body from invaders. The mind and the immune system communicate through the peripheral nervous system and through hormones and cytokines, and this communication enables the immune system to be responsive to psychosocial factors and to signal the brain.
The field of PNI is interdisciplinary and has over the years contributed to the contemporary trend toward viewing health and disease as multifactorial. During the 1960s and 1970s, evidence began to accumulate indicating that the immune system could be influenced by psychological phenomena. In 1964 George F. Solomon and Rudolf Moos proposed that the development of rheumatoid arthritis was related to personality factors, advancing the possibility of psychoneuroimmunological phenomena, and Robert Ader and Nicholas Cohen demonstrated in 1975 that conditioning could affect the immune response by pairing taste with an immunosuppressive drug. Today, there is little doubt that a number of factors—biological, environmental, behavioral, and psychological—can interact to impact the progress and course of many illnesses.
Psychoneuroimmunology research strives to expand the understanding of how psychosocial factors can influence people’s health, either positively or negatively. Research on the influences of psychological factors on the endocrine and immune systems involve examinations of the effects of stressors on these systems, and evidence clearly indicates that psychological and physical stressor exposure can affect the immune system. Stressor exposure also influences the endocrine response, changing levels of hormones such as cortisol. The effects of stressor exposure depend critically on the characteristics of the stressor. Acute stressors that last only minutes can be adaptive as part of a fight or flight response, whereas longer term stressors have less potentially beneficial effects. For example, chronic stressors, such as having a spouse with dementia, have been found to decrease both the cytotoxic and antibody-producing functions of immune cells. Adverse changes in immune functioning have also been associated with divorce, bereavement, unemployment, and other stressful episodes. Research has also demonstrated the importance of healthy social relationships and individual differences that buffer the psychological effects of stress, such as optimism, to better immune function.
Individual differences may not only confer an adaptive impact on the immune system, however. Studies on repression, which is characterized by low self-report of anxiety and avoidance of anxiety-provoking stimuli, but also by high defensiveness, have found associations between repression and poorer cellular immunity. Also, cynical hostility, which reflects suspiciousness, mistrust, and anger, appears to increase the physiological response to stressors involving social interactions and has been associated with increased susceptibility to illness. Clearly, individual differences can impact the immune system in a number of ways.
Studies have shown that stressful experiences can alter elements of the immune response, as well as impact health and disease onset. However, research has not yet convincingly linked these findings together to conclude that alterations in the immune system are in fact the mechanisms through which stressor exposure augments vulnerability to disease.
SEE ALSO Optimism/Pessimism; Stress
BIBLIOGRAPHY
Ader, Robert, and Nicholas Cohen. 1975. Behaviorally Conditioned Immunosuppression. Psychosomatic Medicine 37 (4): 333–340.
Ader, Robert, David L. Felten, and Nicholas Cohen. 2001. Psychoneuroimmunology. Vol. 2. 3rd ed. San Diego, CA.: Academic Press.
Segerstrom, Suzanne C. 2000. Personality and the Immune System: Models, Methods, and Mechanisms. Annals of Behavioral Medicine 22: 180–190.
Segerstrom, Suzanne C., and Gregory E. Miller. 2004. Psychological Stress and the Human Immune System: A Meta-analytic Study of 30 Years of Inquiry. Psychological Bulletin 130 (4): 601–630.
Solomon, George F., and Rudolf Moos. 1964. Emotions, Immunity, and Disease: A Speculative Theoretical Integration. Archives of General Psychiatry 11: 657–674.
Lise Solberg Nes