Some forms of depression may be experienced not as the absence of pleasure but as the presence of emotional pain or disappointment, U.S. researchers said.
Researchers at Stanford University in California recruited both depressed and non-depressed volunteers to undergo brain scans, using functional magnetic resonance imaging, while they participated in an activity in which they won and lost money.
First author Dr. Brian Knutson said when study participants anticipated winning money, both depressed and non-depressed people showed neural activation in the nucleus accumbens, a region implicated in the anticipation of reward.
"Only the depressed participants, however, additionally showed increased activation in the anterior cingulate, a region of the brain that has been implicated in conflict," Knutson said in a statement.
Knutson said "these findings are consistent with formulations that depression involves difficulties in the processing of positive information, and suggest more specifically that depressed people actually experience conflict when they are faced with the likelihood of receiving a reward."
The findings were published in the April Biological Psychiatry.