Laugh out loud - seriously

Social media trends suggest that 99 per cent of videos that go viral are funny ones. The YouTube Gangnam Style video was a hit, not because of its deep Korean lyrics, but because of how ridiculous Psy looks in the video. The same can be said about Rebecca Black's Friday (or Saturday for that matter) and Norwegian band Ylvis's meaningless number What Did The Fox Say? All these videos have one thing in common: they make viewers laugh.
It's a known fact that laughter is a powerful antidote to stress, pain and conflict. Humour lightens the burden and laughter is contagious and is universal.

The biology of laughter
According to Encyclopaedia Britannica, "Spontaneous laughter is a motor reflex produced by the coordinated contraction of 15 facial muscles in a stereotyped pattern and accompanied by altered breathing. Electrical stimulation of the main lifting muscle of the upper lip, the zygomatic major, with currents of varying intensity produces facial expressions ranging from the faint smile through the broad grin to the contortions typical of explosive laughter."
It basically means that we must guffaw at least a few times per day to keep our stress levels in check.
While the human brain does not have a specific laugh centre in the body (at least, according to latest research), it is evident that laughter depends on neural paths arising in close association with the centres in the brain associated with breathing.

Studies have also shown the link between laughter and healthy functioning of blood vessels. There have been theories that prove that laughter has reduced the levels of stress hormones such as cortisol and epinephrine in an individual. A study in 2000 established the link between laughter and heart disease. People with heart disease, it said, were 40 per cent less likely to laugh compared to people of the same age without heart disease.
Laughter also stimulates the respiratory system. It forces us to take in more oxygen and expel more carbon dioxide, which helps us relax better.

What the doc says
Mumbai-based psychiatrist Vihang Vahia, says, "Laughter reduces tension, makes people optimistic." Vahia, however, cautions that too much of anything can be bad. "In some cases, too much of a stimulus (in this case laughter) can cause a seizure in an individual, which can result in death. Therefore one must be in control when s/he laughs."

Laughter and the elderly
Vahias's son Ipsit, director of research at Senior Behavioral Health, University of California, San Diego, says, "Deliberate laughter is a form of aerobic exercise and may help regulate respiration, and boost circulation. Most forms of aerobic exercise have shown to have a beneficial effect on the brain, including improvement in mood, reduced depression and better preserved cognitive function. It can help promote successful ageing."
However, he adds that laughter in the context of laughing clubs or laughter yoga should be performed with the same caution as any other physical exercise and in consultation with a physician.