We laugh when we are happy. Laughter provides us with happiness and is the best medicine available to us, relieving the pain and stress of life. In fact, when we laugh we secrete a neurotransmitter called endorphin, which as the name suggests (endo(inside) + morphine), has the same properties as morphine.
What makes us laugh? The best theory to date is that laughter is an instinctive response to the passing of danger (also called the relief theory). For example, if our ancestor came across a predator but it passed by without noticing him, he would have laughed in response to the relief he felt. Others would see from his laugh that the danger had passed and laugh also (possibly explaining why laughter is contagious).
This theory also explains why humour makes us laugh. When you throw a joke, you are essentially giving the other person a “cognitive riddle” with a logical inconsistency. This inconsistency causes the recipient’s subconscious to become confused: “Why is it funny? Why can’t I understand it?”. As jokes are fundamentally a “surprise” to the other person’s mind, they try to solve it and figure it out whether it is a danger or not. If they get the joke, the inconsistency is solved and the person feels relief (as it has been revealed that the confusion brought on by the inconsistency was not dangerous). Once the confusion passes, the person laughs in response. But if the person does not get the joke, the “danger” has not passed and the person does not laugh. This is the basis of one of the laws of comedians: “if the audience is confused, they do not laugh”.
Laughter is beneficial for your health. Frequent laughter lowers the blood pressure, boosts the immune system, relieves pain and lowers the levels of stress hormones such as cortisol. Laughter is especially good for your mental health, therefore having a five-minute laughter yoga session every day where you just laugh as hard as you can will help you lead a happier life. However, ironically laughter can kill you too. Cases of “death from laughter” have been recorded since ancient Greek times to the modern day. The cause has not been identified but it is known that intense laughter can cause cataplexy, which is a paralysis induced by extreme emotions. It is possible that intense laughter overloads the nervous system and causes a heart attack.
Whatever it is, anything is toxic in excess.