Assessing anhedonia in depression: Potentials and pitfalls

The resurgence of interest in anhedonia within major depression has been fuelled by clinical trials demonstrating its utility in predicting antidepressant response as well as recent conceptualizations focused on the role and manifestation of anhedonia in depression. Historically, anhedonia has been understood as a "loss of pleasure", yet neuropsychological and neurobiological studies reveal a multifaceted reconceptualization that emphasizes different facets of hedonic function, including desire, effort/motivation, anticipation and consummatory pleasure. To ensure generalizability across studies, evaluation of the available subjective and objective methods to assess anhedonia is necessary. The majority of research regarding anhedonia and its neurobiological underpinnings comes from preclinical research, which uses primary reward (e.g. food) to probe hedonic responding. In contrast, behavioural studies in humans primarily use secondary reward (e.g. money) to measure many aspects of reward responding, including delay discounting, response bias, prediction error, probabilistic reversal learning, effort, anticipation and consummatory pleasure. The development of subjective scales to measure anhedonia has also increased in the last decade. This review will assess the current methodology to measure anhedonia, with a focus on scales and behavioural tasks in humans. Limitations of current work and recommendations for future studies are discussed.