Researchers have discovered that laughter might just be the best medicine after all. A new study published in PLOS One found that spontaneous laughter can significantly reduce levels of the stress hormone cortisol, leading to positive effects on overall health.

When the human body responds to stress, whether physical (e.g. illness) or psychological (e.g. anticipation of threat), a system called the hypothalamic-pituitary-adrenal (HPA) axis is activated. The stress hormone, known as cortisol, is released in this setting.

Some studies suggest that spontaneous laughter can reduce cortisol levels. True laughter is intuitive, with laughter-specific brain pathways developing even before speech brain pathways. Laughter and humor have been shown to benefit health, including increasing pain tolerance and improving general well-being in a variety of medical settings.

Although many studies have proposed that laughter may decrease cortisol levels, these studies have often recruited only small numbers of individuals, making it difficult to draw definitive conclusions.

To clarify this further, researchers Caroline Kaercher Kramer (based at the University of Toronto, Canada) and Cristiane Bauermann Leitao (based at the Hospital de Clínicas de Porto Alegre, Brazil) conducted a systematic review and meta-analysis of studies.

This process involved gathering relevant literature and reviewing it as a whole, in order to robustly assess the impact of spontaneous laughter on the stress response, as measured by cortisol levels.

Kramer and Leitao focused on randomized controlled trials (in which participants are randomly assigned to either the experimental or control group) and quasi-experiments (a real experiment but without random assignment).

Four randomized controlled trials and four quasi-experiments were selected, published from 1989 to 2021, containing data from a total of 315 participants with an average age of approximately 39 years.

Laughter was induced by participants in the experimental group watching a comedy film (five studies), undergoing laughter therapy conducted by a trained laughter therapist (two studies), or undergoing self-administered laughter therapy (one study). The control group performed usual non-humorous activities.

Cortisol levels were measured from blood or saliva samples, and the change in cortisol levels before and after laughter was compared in the experimental and control groups.

This is what the researchers discovered. Data analysis revealed a significant overall reduction in cortisol levels (31.9%) induced by laughter, compared to the control group.

Upon further investigation, the authors found that even a single laughter session (lasting 9 to 60 minutes) induced a significant reduction in cortisol levels (36.7%), compared to the control group.

Interestingly, the duration of laughter had no impact on cortisol levels.

“The impact on (the) HPA axis found in our analyzes suggests that authentic laughter has positive effects on overall health, as excessive/prolonged cortisol secretion associated with chronic stimulation of the HPA axis has implications negative on physical and psychological illnesses, including obesity and depression. and chronic pain,” concluded Kramer and Leitao.

The authors reinforced how their findings supported other research demonstrating the benefits of laughter and cortisol reduction.

Laughter has been shown to have a cardioprotective effect (in other words, it protects the heart) by reducing the risk of developing coronary heart disease. The findings also support literature that has highlighted potentially positive metabolic effects of reduced cortisol levels, for example increased stimulation of hair follicles, which ultimately leads to hair growth.

A few limitations should be noted, one being that there are differences in the methods used to elicit laughter between studies. The timing of when cortisol levels were measured in participants varied between studies and may also have influenced the results.

The study, “Laughter as Medicine: A Systematic Review and Meta-Analysis of Interventional Studies Evaluating the Impact of Spontaneous Laughter on Cortisol Levels,” was authored by Caroline Kaercher Kramer and Cristiane Bauermann Leitao.

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