A recent report has stressed that laughing or crying uncontrollably at completely inappropriate times and places, or out of context of the current circumstances, might be a signal of an underlying brain illness like multiple sclerosis, Parkinson’s disease and Alzheimer’s disease.

The report has cited the example of a naval aviator student who would suddenly break out into a hysterical laughter at the most odd of moments. He would laugh in his sleep as well. Later, it was discovered that he was suffering from gelastic seizure, which is a rare form of epileptic episode.

The author of "Laughter: A Scientific Investigation" Robert Provine, who is also a Psychology Professor at the University of Maryland, has stressed that terming oddly timed outbursts of laughing or crying an involuntary emotional expression disorder is not always the right thing to do.

"All laughter is uncontrollable in the sense that we don’t laugh, or cry, on command. Laughter is really unconsciously controlled. We go through life making these uncontrollable utterances. We can try to stop laughing since it can get us into trouble when we laugh at the wrong time. But it’s very hard to produce convincing laughter on command", he said.