Cracking the joke

When the famed journalist and author Norman Cousins was diagnosed with a severe form of arthritis, his doctors gave him only 1 in 500 chance of recovery. Unfazed, he developed an unusual way to combat the disease. Along with megadoses of Vitamin C, he decided that laughter would aid his healing. Cousins watched funny shows such as Candid Camera and numerous comedy films (he was a big fan of the Marx Brothers).

Cousins claimed that laughter had an analgetic effect on him, enabling him to sleep pain-free. Though he later downplayed the role of humour and laugher in his recovery and acknowledged that conventional medicine likely cured him (he took every medicine prescribed by his doctors), Cousins' 1979 book, Anatomy of an Illness as Perceived by the Patient, lunched the laughter therapy movement(Cousins, 1979).

Since Cousins publicised his experiences with laughter therapy, many have joined the 'humour is healthy' bandwagon. You've probably seen headlines about the healing power of humour. Many books, websites, and organisations (e.g., the Association for Applied and Therapeutic Humor) promote this idea, promising that more laughter and humour in your life will lead to better health.

Over the years, advocates have suggested that humour can reduce pain, boost the immune system, improve cardiovascular function, and even cure cancer and AIDS (Martin, 2001; Martin, 2008). Some of these claims are extraordinary – and it's easy to connect humour to any health issue. We also need to be clear what we're talking about here – there are times when we smile or laugh without humour, or find something funny without smiling and laughing. And humour also has a dark side – it can be used to mock others or perpetuate racism and sexism.

Despite these nuances, for most people, humour is a positive experience, and humour, smiling and laughter typically occur together. Each is believed to contribute uniquely to our health. We cannot rely on anecdotal evidence, like Cousins' experience. But there is a fair amount of research on the topic that merits attention, beginning with the effects of humour on the immune system.

Humour and the immune system

There is some evidence that watching a humorous film can boost immunity and reduce allergic reactions (Kimata, 2004a). Typical studies measure changes in allergic responses or antibodies before and after participants are exposed to humour, comparing them to a non-humorous control. A few studies have found increased immune responses after watching a funny film. Interestingly, these effects are not exclusive to humour – they are also observed when people listen to classical music or feel sadness (Martin & Ford, 2018). Conversely,  moderate stress, like writing an email or playing video games, tends to suppress the immune response, increasing allergic reactions (Kimata, 2004b).

However, the effects of humour on immunity are often overstated. For example, one highly cited study found that watching 60-minute comedy video increases the production of several immunity-related components, such as natural killer cells, compared to the control group who quietly sat in a room for an hour (Berk et al., 1989). This study received significant media attention at the time and is frequently referenced by proponents of 'humour is healthy' movement. Yet, what is rarely mentioned is that the experimental and control groups each included only five participants The authors reported their results transparently, but this highlights how easily humour's health effects can be exaggerated.

Humour and pain relief

Perhaps the most robust evidence for humour's therapeutic effects lies in its ability to reduce pain. Exposure to humorous content, such as funny films, tends to increase pain tolerance. A common method involves the Cold Pressor Test, where participants immerse their hand in ice water for as long as they can tolerate. Changes in blood pressure and heart rate are often measured alongside.

Interestingly, neutral stimuli like relaxation music or lectures can yield similar increases in pain tolerance as listening to a comedy performance (Cogan et al., 1987). Importantly, the analgetic effect of humour is tied to genuine emotional response. Researchers distinguish between Duchenne smiles and laughter (associated with genuine joy) and fake smiles and laughter. Only genuine laughter stimulates endorphins release, which provide pain relief  (Dunbar et al., 2012; Zweyer et al., 2004). 

So, while Cousins' experiences were anecdotal, his claim that laughter relieved his pain has some validity. However, it wasn't laughter itself, but the accompanying mirthful emotional response that provided relief. Moreover, such effects are short-lived; Cousins himself acknowledged that laughter gave him only two pain-free hours of sleep.

Other health claims about laughter

Many people believe in the healing power of laughter, and its alleged health benefits gained popularity when an Indian doctor, Madan Kataria, created the first laughter yoga club in 1995. Since its introduction, numerous laughter clubs have been established worldwide, where people gather to laugh as much as possible – even in the absence of humorous stimuli – in the hope of improving their health and happiness.

Proponents of laughter yoga claim that laughing offers many health benefits, but studies on the topic are riddled with methodological problems and low-quality evidence. Overall, the conclusion is that there is insufficient proof to support claims that laughter contributes significantly to mental health (Bressington et al., 2018).

Take for example, the popular claim that laughter functions as a form of aerobic exercise, comparable to intense exercise (Fry Jr., 1992). According to this idea, several minutes of intense laughter – common amongst laughter yoga clubs – can increase heart rate and oxygen consumption, purportedly matching the benefits of using rowing machine or stationary bike for 10-15 minutes. Laugh a lot, and you will have an excuse to skip your morning gym session.

However, lab studies using indirect calorimeter to measure energy expenditure show that natural laughter with friends only increases energy expenditure by 10–20 per cent compared to resting values, burning a maximum of 40 calories (Buchowski et al., 2007). This is equivalent to light activities such as writing or playing cards – not what most of us envision when trying to get into shape. Even when participants are asked to laugh deliberately (as in laughter yoga), calorimeter readings indicate they burn about 3 calories per minute – similar to shaving or cleaning the house (though likely more enjoyable than either of those activities).

Humour and longevity

One curious claim is that humour can prolong life. Like many other proposed health benefits of humour, this claim seems reasonable and, on the surface, makes sense. Being cheerful, having a humorous outlook on life, and laughing frequently could potentially add years to our lives. However, as with many other claims, the evidence does not support this idea.

In the famous and longest-running longitudinal study in psychology, the Terman Study of the Gifted, initiated in 1921, researchers followed gifted children for decades. They found that kids rated by their parents and teachers as having a better sense of humour were more likely to smoke, drink alcohol, and die younger than those with less humour (Friedman et al., 1993). Since this is a correlational study, many confounding factors could be at play. More humorous and cheerful children also tended to be less neurotic, which have led them to take health risks less seriously, engage in riskier behaviours, and discount the dangers of their unhealthy choices compared to their less cheerful peers.

Consistent with this research, which shows that individuals with a greater sense of humor tend to engage in less healthy lifestyle behaviors, another (much shorter) longitudinal study of Finnish police officers found that higher scores on humor scales were associated with greater obesity, increased smoking, and higher risk factors for cardiovascular disease (Kerkkanen et al., 2004).

Comedians might be a useful group to study, as they use humour more often than most people. However, the findings are quite consistent, showing that comedians and comedy writers die younger than actors and other celebrities who aren't entertainers (Rotton, 1992; Stewart & Thompson, 2015; Stewart et al., 2016). In comedy duos, the 'funny man' is significantly more likely to die younger than the 'straight man' (Stewart & Thompson, 2015). As with any correlational study, confounding variables likely play a role. Comedians are more prone to unhealthy lifestyles, drug use, and social pressure, all of which could affect their health more significantly than their sense of humour.

In my own research into improv artists, I found that they report more infectious diseases compared to a matched sample from the general population. This study controlled for factors such as age, BMI, antibiotic use, and neuroticism, a known trait affecting self-reported health (Greengross & Martin, 2018). As with stand-up comedians, it is likely that improv artists experience more frequent social interactions, higher stress, and extensive work-related travel, all of which negatively impact their health, leaving humour with little measurable effect on their well-being.

Most research on longevity and humour has focused on people with either exceptional intelligence (gifted children) or exceptional humour ability (comedians and improv artists). But what about the health benefits of humour for more ordinary people? In one longitudinal study of patients with kidney failure, those with a humorous outlook on life had 31 per cent higher odds of surviving after two years (Svebak et al., 2006). While this suggests that humour might serve as a useful coping mechanism, caution is warranted, as the study included only 41 patients.

Another longitudinal study with a much larger sample of over 50,000 people, followed participants for 15 years. It found that only the cognitive component of humour (i.e., recognising that a humorous event occurs) was associated with lower mortality; the social (saying funny things, making others laugh) and affective (being a mirthful person, having a humorous outlook on life) components showed no effect (Romundstad et al., 2016). Moreover, the association was driven entirely by low-scoring women dying earlier, while high-humour men and women did not live longer. Such findings are, at best, tentative and inconclusive regarding humour's potential health benefits.

The long-lasting effect of a smile

What about the potential health benefits of smiling? Smiling can be seen as a milder form of laughter, lacking most of the physiological changes associated with it. However, smiling may serve as an indicator of positive feelings and, more broadly, a positive attitude toward life –both of which could potentially lead to better health.

One study examined the photographs of 196 baseball players featured in a 1952 baseball almanac (Abel & Kruger, 2010). Decades later, the researchers categorised the intensity and authenticity of their players' smiles and tracked down their survival. After controlling for demographic variables such as age, education, marital status, BMI, and career length, they found that players with more intense Duchenne (genuine) smiles lived longer and were half as likely to die in any given year compared to those with fake or no smiles.

While these findings are encouraging, a subsequent replication study with a much larger sample from the same almanac failed to find any association between smiling and mortality after accounting for birth year (Dufner et al., 2018). Despite its more rigorous methodology, this study has far fewer citations and has received significantly less attention from the media. The earlier study showing positive results, garners more interest – perhaps because people are drawn to the idea of the healing power of smiling.

But not all is lost when it comes to smiling. Another study analysed the smile intensity of individuals in college yearbooks from 1945-2005 and found that those with Duchenne smiles were less likely to divorce decades later (Hertenstein et al., 2009). As with other correlational studies, the exact mechanism behind the association is unclear. It could be that happier people smile more, which helps them navigate marital conflicts and endure long-term relationships. Alternatively, smiley people may have more positive attitudes, allowing them to attract partners who foster stable relationships. Your guess is as good as mine.

Extraordinary claims need extraordinary evidence

There are many popular beliefs about how humour and laughter can make us healthier. I hope this review has highlighted some of the nuances surrounding humour and health. The picture is more complicated than it is often portrayed, and there is little solid evidence to suggest that humour and laughter have significant health benefits. Most claims of health benefits are exaggerated, making for appealing media stories, but much of the research in this area is methodologically flawed. These studies often lack proper controls, rely on correlational data, use small samples, and, above all, demonstrate only small, short-term effects with no clear clinical significance.

Some may ask, 'OK, so the alleged health benefits of humour are inflated – what's the harm?' While humour may seem innocuous, there are potential downsides to believing it can significantly improve health. Comedy may give hope to people desperate to feel better, but it's clearly no substitute for clinically proven treatments.

Second, oversimplification around the health benefits of humour and laughter may discourage researchers from conducting studies in the field, fearing their findings could be distorted by the media or exploited for commercial purposes. As scientists, we must remain open to new ideas while demanding rigorous research that addresses the shortcomings of much of the current work in the field. The same scepticism should apply (Martin & Ford, 2018) to research which extends beyond health benefits to claim that humour facilitate learning, aids memory retention, increases productivity, and more. Extraordinary claims about the power of humour require extraordinary evidence. 

Laugh for very joy…

In 1925, some scientists predicted that, in 100 years there would be nothing left in the world to laugh about ("We'll Laugh for Very Joy," 1925). Thankfully, they were wrong – there are still countless reasons to embrace humour. There is strong evidence that humour is beneficial for mental health, primarily as a coping mechanism to reduce stress. Humour also enhances social relationships and is an attractive trait in potential mates. Even if it doesn't make us significantly healthier, it's fun and enriching, and we should enjoy it for its own sake. But as psychologists, it is only through more robust research that we will ensure the joke isn't on us.

• Dr Gil Greengross is a Lecturer in Psychology at Aberystwyth University.

The Editor of The Psychologist, Dr Jon Sutton, is a Trustee for the Big Difference charity, who run the Leicester Comedy Festival and UK Kids Comedy Festival. The events take place 5-23 February. If you have a psychological perspective on comedy (particularly live) and humour, he would love to hear from you on [email protected].

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