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Ancient and healthy: The Science of Laughter
We all laugh. Some may laugh more than others, but it is a unanimous human trait.
It feels good and brings people together.
Really, laughter needs no introduction, but what is it for?
Laughter is a trait that we share with our distant cousins.
We laugh at jokes (albeit not all jokes). We can also laugh sarcastically, nervously, when we are stressed, or even for no reason at all.
Our laughter may be uncontrollable or maniacal, and it might also be forced, faked, or purposefully prolonged.
The laugh is so pervasive that it can hardly be ignored by scientists; it crosses all boundaries. Humans from every culture on earth laugh. Babies who are blind and deaf, having neither seen someone laugh nor heard the sound of laughter, still laugh.
Something as ubiquitous as this odd expulsion of sound and air must be important.
In this article, we will take a brief look at the origins of laughter and what happens in the brain when we are amused. We will also take a wander through the scientific literature to examine whether laughter has the ability to relieve medical conditions.
The laughter of relatives
Laughter is a trait we share with our nearest cousins, the great apes. This means that it was, more than likely, an ancient invention that has been retained over millennia. As with most things that evolution preserves, it must be useful.
One odd but insightful study involved tickling a variety of ape species and human infants. The researchers then compared the sounds of laughter that were generated. Interestingly, species more closely related to ourselves (such as bonobos and chimpanzees) had more similar acoustic data to humans when compared with our more distant relatives (gorillas and orangutans, for example).
As the authors explain, their data matches "the well-established genetic relationships of great apes and humans."
As social animals go, humans congregate in fairly large groups. One theory has it that laughter (along with speech) helped us to bond more efficiently. Rather than having to physically groom each individual in our tribe, we could stand within earshot and make each other laugh. Bonds could be built at a distance and with multiple players.
Whether this theory holds water or not will be difficult to prove, but there is no question that laughing brings people closer together. Laughter helps to build relationships and, when living in a group on the savannah, bonding successfully can be the difference between life and death.
This ability of laughter to act as social glue also helps explain why humans find it so very easy to identify a faked, forced, or overly prolonged laugh.
Although some jokes may need our full cognitive ability and a dose of lateral thought, the act of laughing itself seems to be a primitive thing.
The neuroscience of laughter
It will come as no surprise that an action as complex, varied, and meaningful as laughter is not limited to a single region of the brain. Researchers have, however, made efforts to understand the range of areas that are involved.
One study, published in the journal Cerebral Cortex, used MRI scans to investigate which regions of the brain were at work. They split participants into three groups: the first group was tickled on the sole of the foot and given permission to laugh, the second group was tickled but told to suppress their laughter, and the final group was asked to laugh voluntarily without being tickled.
In the brains of the first group - participants of which were laughing genuinely - certain regions were activated more consistently when compared with the other two groups. These were:
- ►Lateral hypothalamus - involved in an array of processes, such as promoting arousal and feeding behavior, reducing pain perception, digestive functions, and blood pressure
- ►Parietal operculum - partly responsible for processing senses, such as touch and temperature
- ►Amygdala - involved in processing memories, making decisions, and emotional reactions
- ►Right cerebellum - important in visual attention, language, and imagining the states of others.
In this study, they also measured activation of the periaqueductal gray matter during voluntary and involuntary laughter, but not when laughter was prevented. Interestingly, periaqueductal gray matter is known to play a role in analgesia. In fact, the region is a target for brain-stimulating implants to treat patients with chronic pain.
During laughter, regions of the ventromedial prefrontal cortex are activated, releasing endorphins - which are famed for decreasing pain and increasing euphoria.
Involvement of the hippocampus and amygdala are also worthy of note; these are part of the limbic system, an ancient section of the brain involved in the control of deep-seated emotions, feeding, and other survival-critical roles.
Laughter as medicine
As the philosopher Bertrand Russell once said: "Laughter is the most inexpensive and most effective wonder drug. Laughter is a universal medicine." Over the years, researchers have pitted its abilities against a range of medical conditions.
Recent advances in fields such as psychoneuroimmunology are slowly knitting together psychology, neurological activity, and our hormonal state. A positive frame of mind really does make us physically better. It's not all in the mind; psychology modifies physiology.
Studies specifically investigating the therapeutic effects of laughter are few and far between, and those that are found in the literature tend to use only a small pool of participants, making conclusions tentative. However, their combined results make interesting reading.
Below are some recent studies that have delved into laughter's potential healing powers.
Chronic obstructive pulmonary disease
A study published in Heart & Lung investigated the benefits of laughter for individuals with chronic obstructive pulmonary disease (COPD), a group of progressive conditions that block the airways and make breathing difficult.
The study involved 46 individuals, all of which completed questionnaires assessing their sense of humor, levels of depression and anxiety, quality of life, and recent illness. Roughly half of the participants also completed a "laughter induction study" where lung function, mood, and dyspnea (difficulty breathing) were assessed before and after an amusing or neutral video.
The author's conclusions were sweet and sour:
"Sense of humor among patients with COPD is associated with positive psychological functioning and enhanced quality of life, but laughing aloud may cause acute deterioration in pulmonary function secondary to worsened hyperinflation."
Negative emotional states, such as depression and anxiety, can increase the risk of cardiovascular disease. This has been firmly established. A layperson could easily conclude that, if negative feelings can contribute to vascular problems, positive ones must improve vascular health. A study published in The American Journal of Cardiology set out to see if this really is the case.
The study involved showing either a comic movie or a documentary to 17 participants. Each individual watched both films on different days so that their results could be compared.
They found that both heart rate and blood pressure increased significantly while participants watched the comedy, but not the documentary.
The team also looked at carotid arterial compliance, which is a measure of the artery's flexibility and its ability to endure increases in pressure. Higher levels of compliance are a sign of healthier arteries.
The results showed that carotid arterial compliance increased significantly after watching the comedy, only returning to baseline values after 24 hours.
During the documentary, compliance remained constant.
Although the study was conducted on a small scale, the researchers concluded that: "These results suggest that mirthful laughter elicited by comic movies induces beneficial impact on vascular function."
Research conducted in Japan and published in the Journal of Epidemiology took a slightly different look at a similar question.
The investigators wanted to understand whether there was an association between how often someone laughs on a daily basis and their risk of heart disease and stroke. They analyzed data from 20,934 men and women aged 65 or above.
Individuals who "never or almost never laughed" had a 21 percent higher risk of heart disease than those who laughed daily. Similarly, the prevalence of stroke in those who rarely laugh was 60 percent higher than regular laughers.
Laughter yoga and depression
Laughter yoga has risen in popularity over recent years. In brief, it involves breathing exercises and forcing yourself to laugh. This forced laughter soon turns into genuine mirth as the group realizes how ridiculous they all appear.
A pilot study, published in 2012, evaluated the effects of 10 laughter yoga sessions on six participants across a 4-week period.
They measured heart rate variability (HRV) - which is considered a risk factor for certain health conditions - blood pressure, and mood before and after each session. At the start of the study and just after the final session, the group's longer-term anxiety and depression were also rated.
The authors concluded:
"Participants showed improved immediate mood (vigor-activity and friendliness) and increased HRV after the laughter intervention. Both the laughter and control interventions appeared to improve longer-term anxiety."
A study titled "Effects of laughter therapy on depression, cognition, and sleep among the community-dwelling elderly" was published in the journal Geriatrics and Gerontology in 2011.
In total, 109 participants took part. Roughly half were enrolled in laughter therapy (four sessions over the course of a month), and the others were used as a control. Using questionnaires, they assessed general mental health, depression, self-reported physical health, and sleep quality before and after the trial.
Although the effects were not substantial, the authors concluded: "Laughter therapy is considered to be [a] useful, cost-effective, and easily-accessible intervention that has positive effects on depression, insomnia, and sleep quality in the elderly."
Whether or not laughter carries with it a protective forcefield is still to be confirmed, but there is no denying its importance in human society. Although the evidence in favor of laughter as a medicine is scant, there is no harm in self-medicating while we wait for the data to trickle in.
Date de dernière mise à jour : Jeu 01 nov 2018
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