Sigmund Freud saw it as a "catharsis"or purging of "psychic energy".
Bertrand Russell said: "Laughter is themost inexpensive and effective wonder drug.
Laughter is a universal medicine."
And for Mark Twain: "The human race has only one really effective weapon and that is laughter. The moment it arises, all our irritations and resentments slip away, and a sunny spirit takes their place."