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.


All three systems interact reciprocally, so there is a constant state of flux, carefully tuning the immune system
All three systems interact reciprocally, so there is a constant state of flux,
carefully tuning the immune system

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 and 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.