This is part three of a four-part series reviewing the evidence on how humor influences physiological and psychological well-being. The first article included basic background information, definitions and a review of the theoretical underpinnings for this area of research. The second article discussed use of humor as a complementary therapy within various clinical samples, as well as evidence concerning how a sense of humor influences physiological and psychological well-being. This third article examines how laughter influences health outcomes; including muscle tension, cardio-respiratory functioning and various stress physiology measures.
In summary, the materials reviewed in this section support that the act of laughter can lead to immediate increases in heart rate, respiratory rate, respiratory depth and oxygen consumption. These increases are then followed by a period of muscle relaxation, with a corresponding decrease in heart rate, respiratory rate and blood pressure. The effect of laughter on the so called ‘stress hormones’ of epinephrine, norepinephrine and cortisol is equivocal, with the few studies conducted thus far demonstrating some conflicting results. This is important because it is theorized that if laughter does, in fact, decrease stress hormones, this would be one mechanism that might explain the proposed connection between laughter and immune function, and from there to improved health outcomes.
The investigation into the effects of laughter on the endocrine system and the immune system is clearly an area in which additional research is needed. The next article in this series will review the evidence available thus far concerning how laughter influences various immune system components.
Please also see this article: The Effect of Mirthful Laughter on Stress and Natural Killer Cell Activity.