The exact cause is unknown. But in a recent study, an experimental drug showed signs of halting the disorder in laboratory mice.

VOA: special.2010.05.19

Psychologist Jonathan Rottenberg at the University of South Florida says they wanted to study crying as it happens in everyday life, not in a laboratory.

VOA: special.2009.01.28

The study used brain images taken at Brookhaven National Laboratory in New York State.

VOA: special.2009.09.29

A laboratory was created to study recently discovered opiate receptors in the brain.

VOA: special.2009.02.10