Positive emotional activities have been suggested as modifiers of neuroendocrine
hormones involved in the classical stress response. To detect changes in these components
during a mirthful laughter experience, the authors studied 10 healthy male subjects. Five ...

Main Outcome Measures• N atu ral killer cell activity; plasma immunoglobulins; functional
phenotypic markers for leukocy tes including activated T cells, nonactivated T cells, B cells,
natural killer cells, T cells with helper and suppressor markers, and assessment of plasma ...

... In recent studies of medical and health interventions, including exercise (Berk et al., 1990) and
the eustress of humor associated mirthful laughter, (Berk et al., 1989, 2001) various patterns of
changes in circulating stress mediators, inflammatory mediators, cytokines, and cellular ...

... The specific phys- iological effects of laughter include the following: relaxes muscles (Fry, 1992;
Paskind, 1932); stimulates ... degrees, licenses, and rank can be altered for fun—for example: Ronald
A. Berk, Ph.D ... 83 as a kind of cooling down jocular exercise or mirthful debriefing. ...

... Humor produces an emo- tional response that decreases stress, and laughter stimulates a
physiological effect that decreases stress hormones such as serum cortisol, dopac, and
epinephrine, as well as growth hormone levels in the blood (Berk et al. 1988; Berk, Tan, Fry et ...

... American Journal of the Medical Sciences, 298 (December), 390–396. Berk, LS, Tan, SA,
Napier, BJ, & Eby, WC (1989). Eustress of mirthful laughter modifies natural killer cell activity.
Clinical Research, 37, 115A. Berk, RA (1999). Laughter therapy. ...