Theoretical cycle of anhedonia

One hypothesis of the cycle of anhedonia (loss of interest or pleasure) in patients with depression is illustrated in this image; this hypothesis comes from a series of experiments performed on a sample of psychology students.¹ The students were given the Beck Depression Inventory (BDI), and only those who displayed either high (BDI score >20) or low (<10) depressive symptomatology were included in the study.¹ As well as completing a series of questionnaires, their helping behaviour was tested during the debriefing process when, in what was made to seem like an accident, a researcher dropped a pile of papers near the participant – latency to help, and the degree of help provided was used as a proxy for helping behaviour, and social anhedonia.¹ Higher levels of participants not helping were seen in the high depressive symptomatology group.¹

There have been attempts to assay the effectiveness of newer antidepressants against the symptoms of anhedonia; one such study found that treatment over eight weeks with a melatonin receptor agonist decreased severity scores on depression scales, as well as scores on the Snaith-Hamilton Pleasure Scale that measures anhedonia.³ However, effectiveness on symptoms of anhedonia remains an unmet need in the treatment of MDD.^1,2,3

MDD=major depressive disorder