Content area
Scientific research has shown that laughter may have both preventive and therapeutic values. Health-related benefits of laughter are mainly reported from spontaneous laughter interventional studies. While the human mind can make a distinction between simulated and spontaneous laughter, the human body cannot. Either way health-related outcomes are deemed to be produced. Simulated laughter is thus a relatively under-researched treatment modality with potential health benefits. The aim of this review was firstly to identify, critically evaluate and summarize the laughter literature; secondly to assess to which extent simulated laughter health-related benefits are currently sustained by empirical evidence; and lastly to provide recommendations and future directions for further research.
A comprehensive laughter literature search was performed. A list of inclusion and exclusion criteria was identified. Thematic analysis was applied to summarize laughter health-related outcomes, relationships, and general robustness.
Laughter has shown different physiological and psychological benefits. Adverse effects are very limited and laughter is practically lacking in counter-indications. Despite the limited number of publications, there is some evidence to suggest that simulated laughter has also some effects on certain aspects of health, though further well-designed research is warranted.
Simulated laughter techniques can be easily implemented in traditional clinical settings for health and patient care. Their effective use for therapeutic purposes needs to be learned, practiced, and developed as any other medical strategy. Practical guidelines and further research are needed to help health care professionals (and others) implement laughter techniques in their health care portfolio.
Spontaneous laughter | Simulated laughter | |
Genuine expression of positive emotions | Always | Not necessarily |
Humor-related or humor-dependant | Very often, but not always | Very rarely |
Laughing "at" or "with" others | Commonly "at" | Always "with" |
Personal engagement/effort to think | Often necessary | Rarely necessary |
Presence of "Duchenne laughter/smile"a | Typical (when not fake) | Only when done with a minimum of enthusiasm |
Together with bodily motion | Yes (uncontrolled) | Yes (controlled) |
One's own free will | No, unrelated | Yes, purposeful |
Triggering off stimulus | Identifiable (external) | None (self-induced) |
Contagious | Yes (often) | Yes (very often) |
Self-control on intensity and duration | Minimum or less | Maximum or more |
Mean ratio vocal/consonant sounds | 1:1 (50% of each one)106 | At will |
Most common vocalizations | Ha/ho | At will: |
Evidence of therapeutic value in medicine | Yes (several studies) | Yes (a few studies so far) |
Best dynamics for experimenting laughter | In a group | Alone/in a group |
Laughter technique samples | Playing; clowning; disguising; dancing; singing; having fun, humor, music; by surprise, emotional release, positive emotions or contagion | Laughter yoga exercises, laughter gymnastics; laughter practice; solo laughter |
Table 1 - Health-related laughter types: main characteristics of spontaneous laughter and simulated laughter.
Publications identified | Main health-related outcomes |
Randomized controlled trials | |
Nagendra et al.113 | On healthy IT professionals (both male and female), 20-30min of laughter yoga (n =53) led to a reduction in blood pressure, endocrine stress markers (cortisol levels) as well as perceived level of stress, when compared to the waiting list control group (n =51) |
Shahidi et al.114 | Ten sessions of laughter yoga (n =23) were at least as effective as exercise therapy (n =23) or a control group (n =24), in improvement of depression scores (Yesavage Geriatric Depression Scale) and life satisfaction scores (Diener Life Satisfaction Scale) of elderly depressed women |
Ko115 | One hour of simulated laughter once a week was considered to be useful, cost-effective and easily accessible intervention that had positive effects on depression (Geriatric Depression Scale), insomnia (Insomnia Severity Index), and sleep quality (Pittsburg Sleep Quality Index) in 41 elderly individuals, when compared to a control group (n =61) |
Interventional studies | |
Foley93 | Participants (n =17) rated their mood before and after 1min of forced laughter. Although the participants generally rated their mood as positive prior to the intervention, after forced laughter more participants rated positive affect significantly higher |
Neuhoff94 | Effects of forced laughter on mood were assessed and compared laughter with two other possible mood-improving activities, smiling and howling. While howling did not substantially improve mood, both smiling and laughing did. Moreover, laughter seemed to boost positive affect more than just smiling by 22 adults |
Beckman109 | 15 sessions of simulated laughter significantly increased positive feelings, social identification, optimism, positive emotions, personal efficacy, and morale of 33 healthy employees in the workplace |
De la Fuente-Mochales111 | After 8 laughter therapy sessions, one per week, laughter led to a 55% reduction in pain scores; a 12% increase in functional mobility; and a 50% reduction in depression symptoms and 42% in anxiety symptoms of 107 chronic pain patients (mainly fibromyalgia). They maintained these gains at follow-up (12 months) |
Humor/laughter interventions | |
Walter110 | 20 patients with late-life depression and 20 patients with Alzheimer's disease (AD) were evaluated. Ten patients in each group underwent a humor/laughter therapy group (HLT) once every two weeks for 60min in addition to standard pharmacotherapy, which was given as usual to the other group as standard therapy (ST). The quality of life scores improved both in HLT and ST groups for depressive patients but not for patients with AD irrespective of the therapy group. Depressive patients receiving HLT showed the highest quality of life after treatment and had also improvements in mood, depression score, and instrumental activities of daily living |
Falkenberg112 | Six patients with major depression participated in a group training program specifically designed to enhance humor/laughter abilities. After 8 weeks of training, short-term mood improvement was observed and the patients considered themselves more capable of using humor and laughter as a coping strategy. Acquired humor and laughter skills also helped to sustain the patients' motivation throughout the training period |
Table 2 - Effects of simulated laughter interventions on health-related outcomes.
Introduction
Laughter is an essential component of human happiness, and its absence is a pathology that is related to maladaptive and other dysfunctional behaviors. Scientific research has shown that laughter may have both preventive and therapeutic values. While several kinds of laughter have been described which are depending on various parameters and different fields of the scientific research,1-3 five large groups can be summarized from a medical and therapeutic point of view4 : (1) genuine or spontaneous laughter; (2) simulated laughter; (3) stimulated laughter; (4) induced laughter; and (5) pathological laughter. Spontaneous laughter , unrelated to one's own free will, is triggered by different (external) stimuli and positive emotions. It has been reported that spontaneous laughter causes typical contractions of the muscles around the eye socket (Duchenne laughter/smile5 ). Simulated laughter is triggered by oneself at will (self-induced), with no specific reason (purposeful, unconditional), and therefore not elicited by humor, fun, other stimuli or positive emotions. Stimulated laughter happens as a result of the physical contact or action (reflex) of certain external factors (i.e. to be ticklish, specific facial or bodily motions, by pressing laughter bones6 ). Induced laughter is a result of the effects of specific drugs or substances (i.e. alcohol, caffeine, amphetamines, cannabis, lysergic acid diethylamide or LSD, nitrous oxide or "laughing gas", and more). Lastly, pathological laughter is secondary to injuries to the central nervous system caused by various temporary or permanent neurological diseases and may also occur with certain psychiatric disorders. Pathological laughter is developed with no specific stimulus, is not connected with emotional changes, has no voluntary control of its duration, intensity or facial expression, and sometimes comes with "pathological crying".7
Health-related benefits of laughter are mainly reported from spontaneous laughter interventional studies, although the therapeutic value of laughter would concern in particular the first two types, spontaneous laughter and simulated laughter (Table 1), and to a lesser extent stimulated laughter. Modern laughter techniques are based on the following fundamental principle: through several exercises, activities and dynamics, a person or a group of people is transferred to a feeling of lack of inhibitions to achieve the binomial simulated laughter-spontaneous laughter and to experiment its physical, psychological, emotional and spiritual benefits. While the human mind can make a distinction between simulated and spontaneous laughter, the human body cannot, only the difference in the intensity of the abdominal contractions that are created; therefore, their corresponding health-related benefits are alleged to be alike provided the simulated laughter is done with a minimum of enthusiasm ("motion creates emotion" theory). Simulated laughter is thus a relatively under-researched treatment modality with potential health benefits. Indeed, simulated laughter may lead to a higher "laughter exposure" both by achieving greater intensity and duration at will, or by triggering contagious and turning into spontaneous laughter, which might create greater accompanying psychophysiological changes.
The aim of this review was firstly to identify, critically evaluate and summarize the laughter literature across a number of fields related to health, health care, patient care and medicine; secondly to assess to which extent simulated laughter health-related benefits are currently sustained by empirical evidence; and lastly to elucidate whether certain recommendations for further research are needed so that future directions can be provided.
Review of the literature
Design and methods
A narrative review was conducted. This type of review is particularly useful where the aggregation of data is difficult because diverse definitions, many studies or fields, and different outcomes are being analyzed.8,9 A comprehensive laughter and humor literature search was performed using a variety of electronic databases (Medline, PubMed, Cochrane Library and Google Scholar) and following keywords: laugh; laughing; laughter; laughter yoga; mirth, mirthful; humor; therapy; intervention; mind-body; medicine; health; health care; patient; and patient care. A manual search of additional relevant sources (specific publishers and their journals, and grey literature) was also included. A list of selection criteria was identified: (1) inclusion criteria: simulated laughter intervention main focus of paper; direct or indirect relationship to health-related outcomes; and paper either research or seminal in some form; (2) exclusion criteria: humor research only, non health-related research; textbooks, media-related items; and non-English, non-Spanish publications. All relevant published articles up to 2011 (March) were reviewed. No papers were excluded in respect of quality because of the dearth of literature meeting both the established inclusion or exclusion criteria. Thematic analysis was applied to summarize health-related outcomes, patient outcomes, relationships, and general robustness.10 This review was not funded.
Overall results
Laughter health-related outcomes were identified in the following areas of medicine and patient care (references cited are not exhaustive): oncology11-14 ; allergy and dermatology15,16 ; immunology17,18 ; pulmonology19-21 ; cardiology, endocrinology and metabolism22-26 ; internal medicine and rheumatology27 ; rehabilitation28,29 ; psychiatry and medical psychology30-33 ; anatomy, neurology and imaging34-40 ; biophysics and acoustics41-45 ; geriatrics and aging46-48 ; pediatrics49-51 ; obstetrics52 ; surgery53-55 ; dentistry56-58 ; nursing59-64 ; critical care, palliative and terminal care65-72 ; hospice care73-75 ; home care76 ; general patient care and primary care,77-80 epidemiology and public health,81,82 complementary and alternative medicine83,84 ; and medical and health sciences training.85-87
Laughter has numerous effects involving the muscular, cardiovascular, respiratory, endocrine, immune, and central nervous systems. The research reviewed in this area relates to the impact of laughter on the entire body and can be lumped into the following main physiological effects4,22,88-91 : (1) exercises and relaxes muscles, (2) improves respiration, (3) stimulates circulation, (4) decreases stress hormones, (5) increases immune system's defenses, (6) elevates pain threshold and tolerance, and (7) enhances mental functioning. The psychological effects of laughter relate primarily to it as a coping mechanism and, to a lesser extent, to its enhancement of interpersonal relationships.92 The research available in this area,93-106 somehow larger and much stronger than the evidence for the physiological health benefits, can be summarized as follows: (1) laughter reduces stress, anxiety, tension and counteracts depression symptoms; (2) elevates mood, self-esteem, hope, energy and vigor; (3) enhances memory, creative thinking and problem-solving; (4) improves interpersonal interaction, relationships, attraction and closeness; (5) increases friendliness, helpfulness and builds group identity, solidarity, and cohesiveness; (6) promotes psychological well-being; (7) improves quality of life and patient care; and (8) intensifies mirth and is contagious. The side effects of laughter are very few. In specific cases the appearance of a laughter-induced syncope has been reported.107 Contra-indications are nearly non-existent, however precaution is advised with patients recently released from surgery, with certain cardiovascular or respiratory diseases or glaucoma.
Specific results
As a laughter type, simulated laughter is getting increasingly popular worldwide since it is the foundation of the Laughter Club movement (laughter yoga). Simulated laughter exercises can be focused on the following categories108 : (1) emotional wellness (pantomiming any action and adding laughter on top); (2) physical workout (aerobic training; balance, flexibility, mobility, resistance and strength training, and improving lung capacity); (3) playful behaviors (engaging in playful movements to help dissolve inhibitions); and (4) special techniques (cross-brain exercises; dancing and singing exercises; empowering behaviors and conversations; group games; floor exercises; laughter and ideokinesis; laughing alone; and laughter meditation). The library of simulated laughter techniques is virtually infinite, and by considering many different possibilities, further exercises can be developed and added: to laugh alone, in pairs or in a group; for kids, adults, seniors, or just any patient; safe (anybody can relate); playful (best done once you have warmed up your laughter muscles) and exaggerated (appropriate only once you are in that laughter mindset); to laugh standing up, on a chair, lying on the floor; with or without props; using different body parts; depending on level of physical fitness (from 0 to very fit), underlying health conditions, or preventive or therapeutic aims.
In this review, six interventional studies93,94,109-112 and three randomized controlled trials113-115 were identified experimenting simulated laughter in some form and then assessing its health-related outcomes specifically. Overall, simulated laughter has also shown some quantifiable effects on certain aspects of health. In particular, both physiological and psychological benefits have been reported and the results found in these studies are summarized in Table 2.
Recommendations for future research and practical guidelines
Laughter research challenges
While some authors advocate that the practice of medicine is still an art, and it may not be necessary to do controlled studies and provide evidence-based data to support the therapeutic use of humor and laughter,68 there is a real need for more research in the field. Laughter research designs can be quite challenging. One of the largest methodological problems in laughter research is the failure to distinguish humor from laughter. Humor and laughter are distinct events (although often associated): while humor is a stimulus and can occur without laughter, laughter is a response and can occur without humor.116 It is necessary to distinguish between these variables, as many studies have used a humor stimulus (such as a comic movie) to determine the effect of 'humor' on a health-related outcome, while others look specifically at the effects of laughter on these outcomes. Still others explore different ways to assess sense of humor, in an attempt to analyze whether scoring higher on a sense of humor scale is associated to certain health outcomes. Thus it is crucial that future laughter research includes some measure of subject response to the different stimuli whenever they are used to help elicit laughter, as some individuals who are exposed to a particular (especially humor-centered) stimulus do not always laugh. Laughter also may not be able to be studied at a conventional "active ingredient" or "dose" level. A design to help preclude laughter absence, and to adjust for its intensity, dosage and duration, is to conduct simulated laughter intervention trials. Simulated laughter is entirely achievable and appears to be the most realistic, sustainable and generalizable intervention to be used in future laughter research. Another methodological concern is that of control groups. Larger samples of healthy subjects and trials in different clinical populations are also warranted. Therefore, it may be useful for researchers in an area dominated by psychology to carry out interdisciplinary well-designed studies involving experts from different health care fields.
Future directions
Research on simulated laughter is still in its early infancy. Laughter researchers may also have difficulty defining precise and measurable outcomes for a therapy for which the main effect is often subjective or highly dependent on the skill of the practitioner and the laugher him/herself. Clearly, more groundwork is needed to determine the best methods of assessing and documenting simulated laughter health-related outcomes in different patient populations. However, some remarkable results on the first exact system for the measurement of laughter itself (diaphragm electromyogram) have been published recently.117 Since this measuring system can specify the starting point and duration of laughter precisely of 1/3000s, it will make detailed analysis of the healthy effects of simulated laughter (or any kind) possible in different clinical settings.
Practical guidelines
Health care professionals can play a significant part in eliciting better understanding of laughter benefits in clinical conditions and real-world life for both patients and themselves.118 But like any other skill, the effective use of simulated laughter and other laughter techniques for therapeutic purposes needs to be learned, practiced, and developed as any other medical strategy. Nevertheless, practical guidelines or further advice are needed to help health care professionals (and others) implement laughter techniques in their health care portfolio. In particular, a unique and comprehensive handbook on simulated laughter exercises and a companion book on FUN-damentals (Gendry119,120 ) are already available, and a "Handbook on Laughter Medicine and Therapy" (Mora-Ripoll121 ) is, to our knowledge, the first one published specifically on this subject.
Conclusions
To date there is sufficient evidence to suggest that laughter has positive, quantifiable physiological and psychological effects on certain aspects of health.122-124 However, current empirical data for the benefits associated with simulated laughter is much more limited, and further well-designed research is warranted. Nevertheless, the health community is still very slow in accepting and considering laughter as a healing tool within the complementary/alternative medicines (CAM)125 or lifestyle medicine.126,127 In order to offer patients the benefits of laughter, health care professionals must be willing to break loose from conventional therapeutic constraints, regain their own laughter, and learn the techniques to facilitate laughter in their patients. Laughter deserves a special place in medical practice and daily life. Moreover, proponents of 'positive psychology' have identified humor and laughter as one of the 24 positive personal values and attributes.128,129 Simulated laughter techniques (i.e. "laughter yoga"130 ) can be easily implemented in traditional clinical settings for health and patient care. The following seems to be a good advice for both patients and health care professionals: "add simulated laughter to your working and daily life, remember to laugh regularly, share your laughs and help others to laugh too".122
Conflict of interest
None disclosed.
Acknowledgement
I thank Sebastien Gendry, Director of the American School of Laughter Yoga (www.laughteryogaamerica.com), for his assistance with the classification of simulated laughter exercises into the four categories identified.
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