Anhedonia is amongst the hallmark clinical features of MDD. However, a variety of epidemiological and human experimental research demonstrates that melancholic (or anhedonic) depression varies from other forms of depression. In addition to the DSM-IV definition of melancholic depression, which requires pervasive anhedonic features, both psychometric40–44 and laboratory-based settings7 have been used to examine hedonic capacity. These studies conclude that anhedonia represents a unique and clinically important phenotype.
