2017-10-05

Normally, we laugh because something's funny, but sometimes laughter can be something more serious -- a medical symptom. This sounds a little strange -- what do laughter and sickness have to do with each other? When we laugh, it's usually a sign of happiness. According to the science of happiness, intentional laughter can even uplift our mood and make us happy [source: Lamber]. But every now and then, you'll find yourself waiting in line at the bank or at the grocery store when someone just laughs suddenly and wildly for no apparent reason. He or she may have a tic and may make twitching motions, or may seem slightly disoriented. The person may be laughing and crying at the same time in a way that seems childish or violent. When we laugh unintentionally and repeatedly, we may be experiencing pathological laughter. That's a sign of an underlying disease or medical condition that usually affects the nervous system, and researchers are still learning more about this phenomenon. (Pathological laughter usually isn't associated with humor, mirth or any other expression of happiness.)