The Nascent Science of Psychoneuroimmunology
I. What Psychoneuroimmunology Is
Psychoneuroimmunology is the emerging science of the interaction between the nervous, endocrine, and immune systems. The way in which the nervous, endocrine and immune systems are linked should be easy enough to understand -- at least to anyone who has studied recent military history. The lopsided victory in the Persian Gulf War was largely due to the fact that the allies had effectively knocked out the Iraqi system of command and control with air strikes, preventing Saddam Hussein from ever mounting a well-coordinated resistance. The immune system is, in effect, the body's military, and, like any other military, it needs a system of intelligence, command and control. (In fact, the HIV or AIDS virus uses similar tactics: It disrupts the production of Helper T cells, which function primarily as messengers.(24))
Because the nervous system is the body's normal means of command and control for other systems, such as the skeletal-muscular, digestive and circulatory systems, it would be economical for the immune system to utilize the same communications infrastructure. This is in fact what it does. However, according to earlier twentieth-century medical dogma, it did not. The immune system, about which very little was known, was presumed to be autonomous, having its own communications network -- even though that network had never been discovered.(25)
In Head First, Norman Cousins describes psychoneuroimmunology as follows:
A biology of the emotions is coming into view. For example, discoveries have been made that both the neuroendocrine and immune systems can produce identical substances (peptide hormones, or neuropeptides) that influence both neuroendocrine and immune activity. The two systems also share the same array of receptors with which these substances can interact and transmit their messages.(26)
Cousins depicts how the immune system responds to an attack by a cold or flu virus. Viruses infect us by injecting their DNA into a cell, which in turn replaces the original DNA of the cell. Instead of performing its normal function, the cell metabolism begins replicating the virus within itself, until it finally bursts and releases the new viruses to infect other cells. This process would always be lethal were it not for the immune system, which can destroy viruses. Here is Cousins's play-by-play description of the immune system's defense against these invaders:
According to Cousins, we have only very recently had sufficient knowledge of the immune and nervous systems to begin learning how they interact. What has been discovered is that the immune system is not confined to any particular bodily location or process. Therefore, when asked what sorts of things can influence the immune system, Cousins replies:
Practically everything. The immune system can be affected by biochemical changes in the body, by an invasion of microorganisms, by toxicity, by hormonal forces, by emotions, by behavior, by diet, or by a combination of all these factors in varying degrees. The immune system is a mirror to life, responding to its joy and anguish, its exuberance and boredom, its laughter and tears, its excitement and depression, its problems and prospects. Scarcely anything that enters the mind does not find its way into the workings of the body. Indeed, the connection between what we think and how we feel is perhaps the most dramatic documentation of the fact that mind and body are not separate entities but part of a fully integrated system.(28)
II. The Development of a New Branch of Science
Medical history is filled with breakthroughs that began as accidents. Alexander Flemming was not the first to notice that mold spoils bacteria cultures. In fact, pathologists and researches had been cursing this phenomenon for years. However, he raised some unusual questions with respect to this that led to the discovery of antibiotics. Jenner noticed that milk maids did not get smallpox. His speculation, that their exposure to cowpox, a much milder relative of the disease, seemed to coincide with their apparent immunity to smallpox, led to the development of immunization -- as well as scathing criticism of Jenner by his medical contemporaries.
Psychoneuroimmunology had similar beginnings. In an interview with television commentator Bill Moyers, Dr. David Felten, one of the pioneers in the field, explained how he made his first major discovery:
FELTEN: [It happened] almost by accident. I came to it [psychoneuroimmunology] with an M.D. and a Ph.D. directed toward neurosciences.... One day I was looking through a microscope at tissue sections of liver in order to identify nerves that travel alongside blood vessels. I was having trouble seeing what the cells really looked like, so I said, "Let's go to the spleen. Everybody knows what the spleen looks like." So I started looking at blood vessels and some of the surrounding areas in the spleen. And there, sitting in the middle of these vast fields of cells of the immune system, was a bunch of nerve fibres. I looked at them and thought, what is this? Nerve fibers aren't supposed to talk to cells of the immune system. What are they doing here?
So we cut some more sections, and looked -- and there they were again. We tried other blocks of tissue, and there they were again. They kept showing up again and again. We and others eventually discovered nerve fibers going into virtually every organ of the immune system and forming direct contacts with the immune system cells.
MOYERS: What was the significance of this?
FELTEN: Well it suggested that the nerves might influence the immune system.
MOYERS: So when you were looking into that microscope, were you seeing something about the healing process for the first time?
FELTEN: I didn't realize it at the time, except that I was struck by the possibility that the nerves might be controlling some aspect of the immune response. A student of mine, John Williams, carried out some of the first studies demonstrating this. But in those days it was almost dogma that the immune system is autonomous and doesn't have any outside controls. We were almost afraid to tell anyone for fear people would say: "Oh, jeez, don't you know the work of Blutz and colleagues?" -- or they'd come up with some reference that we had never found and make us look like a bunch of dufuses because we didn't know what we should have known. So we scoured the literature and searched high and low and tried to find every citation on the subject. And the more we looked, the more we realized that if you looked carefully at some of the photographs in other people's publications, you could see nerve fibers sitting out among the lymphocytes -- but nobody ever commented on it.
When we went to the immunology literature, we found that the immunologists had discovered receptors for neurotransmitters sitting on the surface of cells of the immune system, but they couldn't quite make sense of it. Why would a lymphocyte have a receptor for a neurotransmitter? The question just fell by the wayside. Nobody really put two and two together and tried to make a story about the brain having a direct influence on the immune system.
So we joined some of our colleagues, who are immunologists, and started studying immunologic changes that occur when you use drugs to affect the neurotransmitters or when you take the nerves away. Much to our surprise, we found that if you took the nerves away from the spleen or the lymph nodes, you virtually stopped immune responses in their tracks.(29)
The discovery of receptors for neurotransmitters on immune cells was just the beginning. Other research revealed receptors for methione enkaphalin, a natural opiate produced by the body, on T-cell lymphocytes.(30) Enkaphalins and endorphins were previously believed to function primarily as natural anesthetics, i.e., nervous system activity suppressers. It is highly unlikely that these receptors exist on immune cells for decoration. It made more sense that they be there to decode messages distributed by the nervous system.
Still other studies have revealed more connections between the immune and nervous systems. Dr. Branislav Jankovic of the University of Belgrade conducted studies showing the effect of brain lesions on immune responses.(31) Dr. Rudy Ballieux of the University of Utrecht (the Netherlands) showed that immune responses can be proportionately reduced with the power of an electro-shock.(32) Two Swiss doctors, Walter Pierpaoli and Georges J. M. Maestroni, conducted experiments showing ongoing control of the immune system by the neuroendocrine system. For example:
[I]nterference with the cyclical release of the hormone melatonin (released by the pineal gland) profoundly handicaps immunity. Pierpaoli's research has also shown that the immune system has important regulatory effects on the neuroendocrine system.(33)
Another Swiss researcher described a feedback loop between the immune system and the brain:
[A]ctivated monocytes and macrophages produce interleukin-I, which in turn increases corticotropin-releasing factor activity in the hypothalamus, which results in an increase in adrenocorticotropic hormone and corticosterone blood levels, and decreased immune activity.(34)
Disorders in the brain, such as schizophrenia, have also been linked to decreased immune system activity.(35) Sometimes playing with the immune system affects the nervous system. For example, the thymus gland, an immune system organ, secretes a substance that affects the nervous system.(36)
In one sense, the discovery of the connection between the nervous and immune systems has explained how thoughts can heal. Although a direct link between the system that thinks and the one that heals has been firmly established, the discovery raises more questions than it answers. The set of feedback loops between the immune, endocrine, and nervous systems is enormously complex. In fact, each system individually is extremely complex. The more we study the interactions among them, the more we discover how little we know. Few, if any, questions can be answered by a simple formula, at least at the biochemical level.
On the macrobiotic level, we have known how it works for centuries: It simply follows the GIGO (garbage-in-garbage-out) principle: Thoughts of sadness, guilt, depression, fear, and despair tend to make us sick. Thoughts of joy, hope, forgiveness, humor, and enthusiasm tend to make us healthy. Some emotions, such as anger, can affect health in either direction. Up until recently, medical doctors viewed these principles as common knowledge.
However, here it must be emphasized that psychoneuroimmunology begs the question with respect to the mind-body issue of philosophy. What it shows is a brain-body connection. Recent scientific investigations into brain functions have revealed that the brain actually functions as a gland, secreting, combining, and regulating the levels of chemicals, such as endorphins and enkephalins, that serve not only to control pain but also to regulate the immune system and tumor growth. Thus, the brain appears to have regulatory functions along with cognition. Norman Cousins makes this point:
Ever since scientific investigators have begun to probe the structure and function of the human brain, the main research has been connected to consciousness and cognition. Just in the past half-century, as stated elsewhere, new findings have emphasized the glandular role of the brain.(37)
All that psychoneuroimmunology has shown us is that the nervous system, of which the brain is an important part, can be an agent in the maintenance and recovery of health. It never attempts to address the philosophical issue of the relationship between brain activities, on the one hand, and thoughts and emotions, on the other.
The evidence from psychoneuroimmunology is a double-edged sword for advocates of mental healing. Although I believe it provides some convincing evidence for the value of mental healing therapies, it may turn out to be just the excuse materialist skeptics need to continue to ignore the data. Although these skeptics may now have more reason to recognize the value of affirmations and imagery, the effectiveness of these therapies may no longer serve as a counterexample to materialism. All that data, which they have chosen to ignore over the years, may have no philosophical significance anyway. We now have a "natural" explanation of faith healing: The brain is doing it. "Yes," the materialist skeptic can now say, "You should affirm and visualize positive and healing thoughts whenever you are sick, and probably when you are healthy as well. Just do not kid yourself into believing that some purely spiritual entity, such as a soul or God, is involved in the process. As it turns out, what you have called 'mental and spiritual healing' is no more mental or spiritual than the simple act of raising one's right arm. It is the brain within that does the work."
My answer to this argument is that this healing is also no less mental and spiritual than raising an arm. From a philosophical perspective, what psychoneuroimmunology has accomplished is to toss the whole subject of mental healing into the arena of the mind-body debate -- and, as I shall argue later in this essay, rightfully so. The philosophical issue now is not whether psychosomatic healing occurs, but whether what we have called mental healing is really mental at all, and if so, how so.
Notes on Chapter 5
24 Cousins, Head First: The Biology of Hope and the Healing Power of the Human Spirit (New York: Penguin Books, 1990), 76. Return to text
25 Moyers, 215. Return to text
26 Cousins, Head First, 37 Return to text
27 Cousins, Head First, 36. Return to text
28 Cousins, Head First, 35 and 37. Return to text
29 Moyers, 213-4. Return to text
30 Michael Murphy, 20. Return to text
31 Cousins, Head First, 273. Return to text
32 Cousins, Head First, 274. Return to text
33 Cousins, Head First, 275-6. Return to text
34 Cousins, Head First, 276. Return to text
35 Cousins, Head First, 297. Return to text
36 Murphy, 20. Return to text
37 Cousins, Head First, 74. Return to text