TO READ: Happy Faces Trigger Less in the Brains of Depressed People
When you're depressed, you know it's hard to put on a smile -- and it can even feel difficult to react to smiling people around you. Now brain research shows that depressed people do have real impairments in the ways they process happy faces.

In a recent study, depressed people were slower and less accurate at "processing" -- in this case, detecting the gender of -- happy faces than were healthy people, as shown by functional MRI. But after eight weeks on Prozac, and improvement in symptoms, this ability returned. On another task, responding to increasingly happy faces, the emotion-processing regions of the depressed brains were less active than they were in healthy people's brains. In this case, the difference was not improved by the antidepressant.

Being able to recognize and respond to other people's emotions is a crucial part of interpersonal relationships. These different responses demonstrate that it's not a personal failing to have trouble reacting to a friendly person when you're depressed, but a measurable neurobiological trait of the illness.

For more information: Am J Psychiatry 164:540-542, April 2007.