Is laughter a form of therapeutic medicine?
I think the cortisol number is the one to sit with for a moment. A one-third reduction in your primary stress hormone from something as simple as laughing is the kind of result that makes you wonder what else we've been overlooking. We spend billions on supplements and gadgets to chase calm, and here's a free activity that has been hiding in plain sight since before we were human.
The meta-analysis side is encouraging too, but I'd want to know more about what "laughter therapy" actually looked like in those 33 trials. Was it laughter yoga, comedy videos, improv classes, or a mix? The mechanisms probably differ, and the dose matters. Can you get the same cortisol drop from a polite chuckle as from a full belly laugh? I suspect not, but the data would be fascinating.
Where I land is this: laughter isn't a replacement for proper medical care, but it's a remarkably low-cost adjunct with essentially no side effects. The fact that it modulates the stress axis, which touches nearly every system in your body, makes it more interesting than a mere mood booster. I'd love to see a study that pairs laughter therapy with heart rate variability monitoring to see how deep the physiological effects really go.