This is a great article from Psychology Today looking at the benefits of self initiated laughter which is exactly what we do in Laughter Workshops and clubs.
Here is an extract but it really is worth reading the whole article:
“Long ago, Indian yogis intuitively struck upon the physiological and psychological benefits of spontaneous voluntary laughter and developed Hasya yoga. The basic premise of Hasya yoga is that self-initiated, simulated laughter done in a group quickly turns into genuine and contagious laughter.
The benefits of laughter are believed to be rooted in our nervous system. By putting the cart before the horse with self-initiated laughter, you tap into an innate feedback loop. Any type of laughter stimulates diaphragmatic breathing, activates the parasympathetic nervous system, and triggers the “tend-and-befriend” response linked to healthy tone in your vagus nerve. Just ten minutes of laughter is sufficient to trigger mental and physical health benefits.”