Psychoneuroimmunology (PNI), is a relatively recent branch of science that enforces beliefs that physicians have held for many centuries, perhaps well before the times of the ancient Greeks. The premise is that a patient's mental state influences diseases and healing. Specifically, PNI studies the connection between the brain and the immune system.
The term psychoneuroimmunology was coined by Robert Ader, a researcher in the Department of Psychiatry at the University of Rochester Medical Center in Rochester, New York. In the 1970s, studies by Ader and other researchers opened up new understandings of how experiences such as stress and anxiety can affect a person's immune system.
In the 1970s, Ader performed experiments on lab rats, which showed that environmental factors could impact the immune system. Ader's work went against accepted scientific knowledge, which held that the immune system was not related to other bodily systems, and had no way to physically interact with the nervous system. However, other studies confirmed Ader's findings. The field of PNI blossomed, and hundreds of studies explored various interactions between the immune system and other mental and physical processes.
Many PNI studies have focused on how stress, hostility, and depression impact the immune system. Many conditions such as heart disease, osteoporosis , arthritis, delayed wound healing, and premature aging , are related to stress and negative emotions. Fewer studies have been aimed at showing the benefits of happiness, or positive emotions, on health (perhaps because this is more difficult to test).
Many doctors have noted that a patient's desire to get well is related to the outcome of a disease. Clinical anecdotes recount cases of miraculous healing for no demonstrable reason, or cases where a terminally ill patient held on for months longer than expected to make it to a daughter's wedding or other important occasion. Faith in the physician (or shaman or other healer) has also long been thought to influence healing. The ancient Greek physician Galen wrote, "He cures most successfully in whom the people have the most confidence."
The placebo effect is also a curious aspect of healing. A placebo is a sugar pill or other non-active prescription, which might be given so that the patient thinks he or she is being treated medically. The actual incidence of the placebo effect is difficult to measure, but some researchers believe that as many as one-third of all patients will improve on a placebo.
More than a particular therapy, PNI is a field of research. However, PNI has explored the benefits of many nontraditional or holistic approaches to healing. These include psychotherapy and counseling for people with cancer , and biofeedback and relaxation therapies to reduce stress. It is possible that PNI studies will lead to the discovery of new ways to enhance the immune system, just as it has already shown new ways the immune system can be suppressed. PNI gives credibility to many long-held folk beliefs about the effect of the mind on disease and healing. By demonstrating the physical means by which the mind influences the body, and vice versa, PNI provides a measure of validity to holistic approaches to healing.
Psychoneuroimmunology provides a scientific framework for researchers to investigate the aspects of healing that go beyond standard clinical therapy. PNI researchers look for the physical links that allow the immune system to respond to psychological factors, such as the will to live to a certain date. They look at the ways that mental states, such as hopelessness, can signal the immune system to lower the body's defenses.
Research & general acceptance
Though many scientists were at first skeptical of the findings of PNI, by the start of the twenty-first century the field gained wider credibility. A great deal of new research is being carried out, and there are several academic journals devoted to PNI. Researchers emphasize that they are not simply providing scientific backing for beliefs that happy people live longer, or that people who hold in their anger give themselves cancer. Instead, they are discovering how the immune system communicates with the neurological and endocrine systems.
Some studies focus on the function of cytokines, which are substances secreted by cells of the immune system. The two main classes of cytokines are pro-inflammatory (producing inflammation) and anti-inflammatory (fighting inflammation). Studies of cytokines show that psychological factors such as stress depress the immune system, but that deviations in the immune system can also trigger psychological and behavioral changes. The communication goes both ways. A person, who is fighting infection, perhaps from a cold, undergoes behavioral changes like fatigue , irritability, and loss of appetite. PNI maps complex interactions among the body's systems. Factors studied include mood, illness, immune response, susceptibility to disease, and maintenance of health.
In the early years of the twenty-first century, the United States Public Health Service funded hundreds of research grants in the field of PNI. PNI has been particularly enlightening for researchers and caregivers who deal with people who have cancer, as well as depression.
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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
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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