Modulation of neuroimmune parameters during the eustress of humor-associated mirthful laughter.

CONTEXT Humor therapy and the related mirthful laughter are suggested to have preventive and healing effects. Although these effects may be mediated by neuroendocrine/neuroimmune modulation, specific neuroimmune parameters have not been fully investigated. OBJECTIVE To determine the efficacy of mirthful laughter to modulate neuroimmune parameters in normal subjects. DESIGN A series of 5 separate studies based on a multivariate repeated measures design, with post hoc simple contrast analysis. SETTING The schools of medicine and public health at Loma Linda University, Loma Linda, Calif. SUBJECTS 52 healthy men. INTERVENTION Viewing of a humor video for 1 hour. Blood samples were taken 10 minutes before, 30 minutes into, and 30 minutes and 12 hours after the intervention. MAIN OUTCOME MEASURES Natural killer cell activity; plasma immunoglobulins; functional phenotypic markers for leukocytes including activated T cells, nonactivated T cells, B cells, natural killer cells, T cells with helper and suppressor markers, and assessment of plasma volume and compartmental shifts; plasma cytokine--interferon-gamma; and total leukocytes with subpopulations of lymphocytes, granulocytes, and monocytes. RESULTS Increases were found in natural killer cell activity (P < .01); immunoglobulins G (P < .02), A (P < .01), and M (P < .09), with several immunoglobulin effects lasting 12 hours into recovery from initiation of the humor intervention; functional phenotypic markers for leukocyte subsets such as activated T cells (P < .01), active cytotoxic T cells (P < .01), natural killer cells (P = .09), B cells (P < .01), helper T cells (P < .02), uncommitted T cells with helper and suppressor markers (P < .02), helper/suppressor ratio (P = .10) with several leukocyte subset increase effects lasting 12 hours after the humor experience; the cytokine interferon-gamma (P = .02), with increases lasting 12 hours; total leukocytes (P < .05), with specific subpopulation lymphocytes during the intervention (P < .01) and 90 minutes into recovery (P < .05); and granulocytes during the intervention (P < .05) and 90 minutes following the intervention (P < .01). CONCLUSION Modulation of neuroimmune parameters during and following the humor-associated eustress of laughter may provide beneficial health effects for wellness and a complementary adjunct to whole-person integrative medicine therapies.