Anhedonia across borders: Transdiagnostic relevance of reward dysfunction for noninvasive brain stimulation endophenotypes

Abstract

Introduction Anhedonia is a transdiagnostic psychopathological dimension, consisting in the impaired ability to experience pleasure. In order to further our understanding of its neural correlates and to explore its potential relevance as a predictor of treatment response, in this article we systematically reviewed studies involving anhedonia and neuromodulation interventions, across different disorders. Methods We included seven studies fulfilling inclusion/exclusion criteria and involving different measures of anticipatory and consummatory anhedonia, as well as different noninvasive brain stimulation interventions (transcranial magnetic stimulation and transcranial direct current stimulation). Studies not exploring hedonic measures or not involving neuromodulation intervention were excluded. Results All the included studies entailed the use of rTMS protocols in one of the diverse prefrontal targets. The limited amount of studies and the heterogeneity of stimulation protocols did not allow to draw any conclusion with regard to the efficacy of rTMS in the treatment of transnosographic anhedonia. A potential for anhedonia in dissecting possible endophenotypes of different psychopathological conditions preliminarily emerged. Conclusions Anhedonia is an underexplored condition in neuromodulation trials. It may represent a valuable transdiagnostic dimension that requires further examination in order to discover new clinical predictors for treatment response.

Recovering from depression with repetitive transcranial magnetic stimulation (rTMS): a systematic review and meta-analysis of preclinical studies

“…The effectiveness of rTMS in healthy models compares with human studies involving non-depressed patients and healthy subjects. For example, left human DLPFC stimulation has been demonstrated to reverse hedonic tone dysfunction in addicted subjects 62 , as well as to induce a more pronounced sensitivity to rewarding stimuli in healthy subjects 63,64 . Also, rTMS appeared to selectively reverse depressive-like symptoms while effects on other domains (e.g., anxiety) were rather mixed.…”

“…Stress models of depression, while well-validated in preclinical research, encompass a broad array of symptoms thus possibly diluting specific target treatment effects and introducing bias when examining biological changes associated with rTMS. Narrower phenotypes may capture the biological effects of rTMS and improve prediction of treatment response 63 . The DSM-5 definition of MDD likely represents an aggregate of different and probably highly diverse disease subtypes, each of which should be studied independently and might require specific therapeutic strategies 76 .…”

Hopelessness, Dissociative Symptoms, and Suicide Risk in Major Depressive Disorder: Clinical and Biological Correlates

“…The former represents the inability to experience pleasure or interest in almost all activities of daily life and seems to be a transdiagnostic dimension which is not only interesting for studies on MDD [37]. The latter consists of negative expectations about the future, which could involve the self and others, where subjects find it impossible to solve their problems, so that they never reach their life goals [3].…”

Anhedonia in Major Depressive Disorder (MDD) is Reduced by Transcranial Magnetic Stimulation (TMS)

“…Spano et al suggest that anhedonia may be a "transdiagnostic psychological dimension" and speculates that the presence of anhedonia may indicate a predisposition to respond to TMS treatment [6]. We cannot comment on these broader points but provide important information on anhedonia in MDD.…”

“…Spano et al suggested anhedonia as a "transdiagnostic psychopathological dimension", which may respond to non-invasive brain stimulation (NIBS) [6]. They also suggested that when anhedonia is a core feature of a mental disorder, this may indicate the parent disorder will respond to NIBS.…”