Laughter as a medicine?

As we all are accustomed to the saying that laughter is the best medicine, has this ever been true to anyone in the application? Has this laughter medicine, as they say, has cured anyone of their chronic and terminal illnesses, let’s leave these illnesses has it ever treated an underlying disease like the flu or even the common cold that we all caught? I guess no one has heard of any of these things, so let’s look into further what....