This Quartz article pulls together medical research from around the world on the health benefits of laugh therapy. Excerpt:
In Japan, healthy elderly people have shown significantly increased bone mineral density and improved moods after once-weekly therapeutic laughter exercise sessions of 30-minutes for three months. Iranian doctors who studied the effect of laughter therapy on elderly subjects have also concluded that it improved general health. And research on US cancer patients has linked induced laughter to increased Natural Killer (NK) cell activity. These cells are instrumental in fighting disease, and that same boost was seen in NK cell activity when laughter was induced in healthy patients, too.
Read more at the link below, then have a laugh session of your own: