Anticipatory Reward Deficits in Melancholia
thesisposted on 2015-10-20, 00:00 authored by Huiting Liu
Dysfunctional reward processing has long been considered an important feature of major depressive disorder (MDD). However, empirical findings on reward processing and MDD remain mixed. Depression is a heterogeneous disease and the nature of this heterogeneity may contribute to the inconsistent empirical findings on reward dysfunction in MDD. The current study examined one source of heterogeneity, melancholic symptoms, and its association with reward processing. In 254 people, EEG alpha asymmetry was measured during a behavioral reward task as an indicator of reward processing. Melancholic depression was measured categorically (DSM diagnosis) and dimensionally (Hamilton Endogenomorphy Scale). Results showed that a categorical definition of melancholia did not predict reward processing; however, a dimensional definition did, with higher melancholic symptoms predicting reduced reward anticipation. Importantly, the effects of melancholic symptoms on reduced reward anticipation remained above and beyond overall depressive symptoms. These results suggest that dysfunctional reward processing may only be associated with melancholic symptoms, not depression in general. If replicated, this finding could have important implications for MDD treatment and intervention.