Question: how does crying work

Joseph Devlin answered on 25 Mar 2010:

To be honest, I really don’t know but a colleague of mine answered a similar question for Bang Goes the Theory last season so I will shamelessly lift his excellent answer and include it here. All credit to Steven Watterson from Edinburgh:

Obviously as cool, calm, clinical scientists, we never cry. Not even when our experiments refuse to work and we’re reduced to a frustrated, shaking mess in the corner of the lab. But from reading through the studies, it’s clear that tears have three roles: they keep our eyes moist and lubricated, they wash out irritants like dust and they are a response to extreme emotional stress, usually joy or sadness.

Tears contain water, electrolytes and immune proteins that help to keep the eye free from infection. That explains the first two reasons. But why we produce them after experiencing something sad is not well understood. The opinion of most scientists is that, instead of being a superfluous by-product of emotional stress, tears have evolved into an important way to signal our distress to those around us. For young babies, for example, this is one of the few ways they have to communicate.

Some scientists have speculated that shedding tears is a way for the brain to relieve emotional stress. Amongst some stroke patients who experience recurring and frequent crying, tests have shown that drugs that control the levels of serotonin (a neurotransmitter that can affect mood and relieve depression) in the brain can reduce their susceptibility to crying.