In psychology, anhedonia (< an- + Greek h?don? pleasure ?????) is an inability to experience pleasure from normally pleasurable life events such as eating, exercise, and social or sexual interaction.Anhedonia is recognized as one of the key symptoms of the mood disorder depression according to both the Diagnostic and Statistical Manual of Mental Disorders (DSM) and the International Statistical Classification of Diseases and Related Health Problems (ICD). Other than anhedonia, the DSM considers only depressed mood to be a key symptom. The ICD lists both depressed mood and fatigue or loss of energy as the other key symptoms. Anhedonia is also seen in schizophrenic disorders and other mental disorders.
Researchers theorize that anhedonia may result from the breakdown in the brain's reward system, involving dopamine pathways. Two 2005 studies by Paul Keedwell MD of King's College found that certain sections of the brain in depressed subjects had to work harder to process happy t