Dr Lee Berk, associate professor of Health Promotion and Education at Loma Linda University in California, began researching the benefits of laughter in the late 1970s.

He observed that laughter could reduce the effects of the stress hormone cortisol. Berk’s research also revealed that laughter can increase levels of natural killer cells, a type of white blood cell, which are needed to fight off viruses and tumour cells and keep the body healthy.

In a laboratory study, subjects were falsely led to believe that they would receive an electric shock after 12 minutes.

While they waited for the shock, they were played either a funny tape recording, one that wasn’t funny, or no tape at all, while markers of anxiety were measured. Those who listened to the funny tape rated themselves less anxious than the other two groups.

A study published in 2014 looked at the impact of laughter yoga sessions on the general health of 38 male nursing students. The participants were assigned either one hour of laughter yoga a week, or no intervention.

Overall, the group who took part in the laughter yoga showed improvement in their general health, with a reduction in sleep disorders, anxiety and depression. While the results are promising, note that this research was only carried out on men.

A 2012 study investigated whether laughter therapy could have wellbeing benefits for women going through menopause. Subjects participated in five 30-minute sessions of laughter therapy with results measured against a control group. A series of questionnaires revealed that laughter therapy helped increase optimism and self-esteem and reduce depression for menopausal women, compared to the control group.