Anhedonia in depression symptomatology: Appetite dysregulation and defective brain reward processing

Anhedonia is an elusive symptom in depression symptomatology. The present review frames the notion of anhedonia as reduced ability to experience pleasure and diminished sensitivity to rewarding stimuli such as palatable food or social interaction within the context of appetite dysregulation in depression, addressing the main neural networks involved in the alteration of brain reward processing. This circuit-based framework focuses on selected brain regions such as lateral hypothalamus, ventral pallidum, lateral habenula and mesocorticolimbic target areas such as nucleus accumbens and ventral tegmental area. The examination in particular of the role of dopamine, orexin and GABAergic neurotransmission is complemented by the exploration of the endocannabinoid signaling as homeostatic, anti-stress system and its relevance in depression pathophysiology and anhedonia symptoms.