Laughter-inducing therapies: Systematic review and meta-analysis.

Rationale: Laughter-inducing therapies are being applied more regularly in the last decade, and the number of scientific reports of their beneficial effects is growing. Laughter-inducing therapies could be cost-effective treatments for different populations as a complementary or main therapy. A systematic review and meta-analysis has not yet been performed on these therapies for different populations and outcomes, but is needed to examine their potential benefits. This research aims to broadly describe the field of laughter-inducing therapies, and to estimate their effect on mental and physical health for a broad range of populations and conditions.

Method: A systematic review of the field was undertaken, followed by a meta-analysis of RCTs and quasi-experimental studies. The systematic review included intervention studies, one-session therapies, lab studies and narrative reviews to provide a broad overview of the field. The meta-analysis included RCTs or quasi-experimental studies that assessed multi-session laughter or humor therapies compared to a control group, performed on people of any age, healthy or with a mental or physical condition. English and non-English articles were searched using PubMed, Web of Science, EBSCO and EMBASE. Search terms included laugh(ing), laughter, humo(u)r, program, therapy, yoga, exercise, intervention, method, unconditional, spontaneous, simulated, forced. Studies were classified as using humor ('spontaneous' laughter) or not using humor ('simulated' laughter).

Results: This systematic review and meta-analysis suggests that (1) 'simulated' (non-humorous) laughter is more effective than 'spontaneous' (humorous) laughter, and (2) laughter-inducing therapies can improve depression. However, overall study quality was low, with substantial risk of bias in all studies. With rising health care costs and the increasing elderly population, there is a potential for low-cost, simple interventions that can be administered by staff with minimal training. Laughter-inducing therapies show a promise as an addition to main therapies, but more methodologically rigorous research is needed to provide evidence for this promise.