Book T of C
Chap T of C
This is the 2007 version. Click here for the 2017 chapter 14 table of contents.
Today, a new field is allied with psychosomatic medicine in its search for mind/body interactions. Psychoneuroimmunology (PNI) is the study of psychological and neural influences on the immune system. When it was first formed, this field created a great deal of excitement. It promised to shed light on phenomena as diverse as nasal congestion and faith healing. However, research has often produced ambiguous results.
What is PNI? What was a demonstration of immune system conditioning?
A simple demonstration of how learning can affect immune system response was in Chapter 5 (p.233). Researchers at the University of Alabama medical school exposed mice to the odor of camphor before injections of a chemical that increased NK (Natural Killer) cell activity. After nine pairings, the odor alone stimulated NK cell activity.
Natural Killer cell activity is interesting to researchers because NK cells (a type of macrophage) are a vital part of the immune system. Macrophages fight off invaders such as bacteria, viruses, and even cancer cells. The illustration below shows a macrophage attacking a cancer cell. The cancer cell is the small globular object in the foreground with puncture wounds in it.
A macrophage attacks a cancer cell.
If macrophage activity is subject to classical conditioning, this might explain some psychological influences on healing. However, despite the promising animal studies, no research on humans has yet shown a direct link between psychological treatments, macrophage activity, and measurable effects on health.
What is evidence that stress can affect healing?
One way in which psychological factors can influence health is through their effect on stress. Highly negative life events can affect health. For example, people who were involved in the care of relatives with Alzheimer's Disease (a highly negative life event) did not heal as fast when they were wounded. "Caregivers took an average of 9 days or 24% longer than controls to completely heal a small, standardized wound" (Kiecolt-Glaser, Page, Marucha, MacCallum, and Glaser, 1998). The effect of stress is clearly relevant to human health in several ways, so stress is discussed in its own section later in this chapter.
Cancer is combated by the immune system, so there is hope that psychological techniques can help combat cancer. Many techniques are already in use; for example, cancer patients often use imagery to visualize the immune system fighting or destroying cancer cells. However, as Cohen and Herbert (1996) note, the research on cancer and psychological healing tends to be inconsistent and hard to interpret.
A typical example of PNI research is that of Fawzy and colleagues (1993). They studied 66 patients with malignant melanoma, randomly assigned to treatment or no-treatment conditions. The "treatment" was education, stress management, coping skills, and discussion, all conducted in six 90-minute sessions. "Six months after the intervention ended, participants in the intervention group showed reduced psychologic distress, enhanced immune function (increased NK activity), and changes in immune cell counts (decreased T cells, increased lymphocytes) when compared with patients in the control group. The intervention also decreased recurrence and increased survival as assessed six years later."
That sounds hopeful. However, "alterations in immune outcomes...did not explain the intervention's effect on mortality." In other words, the people who survived longer were not necessarily the ones with increased immune system activity six months after the intervention.
Another study (Spiegel and colleagues, 1989) involved 58 patients with metastatic breast cancer who were randomly assigned to treatment or no-treatment groups. The intervention consisted of weekly 90-minute meetings focused on problems associated with terminal illness and ways to improve relationships. "Ten years later, there was an 18-month survival advantage associated with the intervention." However, immune responses were not measured, so these results cannot be related directly to psychological effects on immune system activity.
These two studies are typical in that psychological interventions typically do have a positive effect on health. However, the effect can seldom be related in a straightforward way to immune system responses.
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