Why do we cry when we are sad?

Humans produce three kinds of tears — basal tears that keep the eyes moist, reflex tears that flush out irritants, and emotional tears triggered by strong feelings. Emotional tears are chemically distinct, containing higher levels of stress hormones such as cortisol and the natural painkiller leucine enkephalin, which has led some researchers to suggest crying helps the body shed stress chemicals and self-soothe. Beyond any internal effect, crying is a powerful social signal: visible tears communicate distress and vulnerability to others and tend to elicit empathy, comfort, and support, strengthening social bonds. Crying activates the parasympathetic nervous system, which can produce a calming, recovering effect after the initial upset. Emotional crying appears to be uniquely human, and though it can feel embarrassing, it plays an important role in emotional regulation and human connection.