New study suggests that both emotions and memory are affected

http://mentalhealth.about.com/health/mentalhealth/library/weekly/aa052101a.htm?PM=n3053001j0-1

21st May 2001
Leonard Holmes, Ph.D.

We are gradually understanding more about the complex interactions between mental health and physical health.  Many studies have shown that positive emotions can enhance immune response, while stress can suppress the immune system.  Now a Hebrew University study has found that memory and mood can be disturbed when the immune system is activated to fight infection.

Abraham Reichenberg and Raz Yirmiya and their colleagues injected 10 healthy male volunteers with a low dose of an endotoxin, a bacterial toxin that triggers the immune system but is ultimately harmless to the patient and causes no feelings of sickness. Ten males received a placebo of saline solution. The subjects responded to the endotoxin by producing cytokines, a group of proteins produced by white blood cells to fight off disease.

Both groups were given mood and memory tests 1, 3 and 9 hours after their injections. The study was repeated 10 days later with the conditions reversed - placebo group received treatment and the treatment group served as the control group.

Reichenberg and Yirmiya found that in each trial, the group of patients who received the injection showed a significant short-term increase in depressive symptoms 3 to 4 hours after receiving the endotoxin. By 9 hours later, the groups reversed themselves with the endotoxin group having lower levels of depression than the control group. Anxiety levels also increased 1 to 2 hours after patients received the injection, but this affect was not sustained. Neither mood change reached clinical levels of depression or anxiety, although they were both statistically significant.

In addition to the changes in mood, the researchers in this study also found a decline in memory function among the subjects whose immune systems were activated.  These changes lasted for the full 10 hours of the study. The authors report that these findings are consistent with prior research reporting a memory loss in patients with elevated cytokines - such as those who take interferon and similar drugs for cancer treatments and patients with viral infections.

Is this the effect of the endotoxin itself or of the immune system gearing up to fight infection?  Further research may be needed to establish exactly what is happening here.  We already know some things about emotions and the immune system.  Some studies have shown that positive emotional experiences such as laughter enhance the immune system.  A recent article about the uses of humor with cancer patients described the immune changes due to laughter as including:

the initiation of the spontaneous blastogenesis of lymphocytes, increased numbers and activity of natural killer cells, and increased numbers of cytotoxic and helper T cells, as well as B cells. Natural killer cells are lymphocytes that engage in cytolytic activity against tumor cells, and B and T cells are essential to the immune response.

Studies have shown that levels of salivary IgA, an antibody that helps fight upper respiratory disease, were elevated after the subjects had watched a humorous film. Humor and laughter also raise levels of the antibodies IgM and IgG, and of complement C3, all of which enhance the inflammation, chemotaxis, and lysis of target cells. Laughter increases levels of interferon gamma, which inhibits virus replication, promotes antigen processing, and activates macrophages. 8 Thus, an immune system that has been weakened by disease and its treatment, and burdened with adverse emotions, may be somewhat renewed in laughter. (Patillo and Itano, 2001)

Clearly the relationships between our emotions and our immune systems are complex.  Positive emotions can sometimes enhance immune functioning, while immune system activation can cause temporary depression, anxiety, and memory loss.  We are beginning to understand some of the details about these complex interactions, but we are far from a comprehensive understanding of the interactions among aspects of the mind and body.  As more of these relationships emerge I will discuss them here.  Please share your thoughts on the Forum.