A parallel-arm, randomized trial of Behavioral Activation Therapy for anhedonia versus mindfulness-based cognitive therapy for adults with anhedonia

Background: Anhedonia, deficits in motivation and pleasure, is a transdiagnostic symptom of psychopathology and negative prognostic marker. Methods: In this randomized, parallel-arm clinical trial, a novel intervention, Behavioral Activation Treatment for Anhedonia (BATA), was compared to an individually administered Mindfulness-Based Cognitive Therapy (MBCT) in a transdiagnostic cohort of adults with clinically significant anhedonia (ClinicalTrials.gov Identifiers NCT02874534 and NCT04036136). Participants received 8-15 individual psychotherapy sessions, once weekly, with either BATA (n = 61) or MBCT (n = 55) and completed repeated self-report assessment of anhedonia and other internalizing symptoms. Results: Indicators of treatment feasibility were similar across conditions, though MBCT showed a trend towards greater attrition rates than BATA, with an adjusted odd's ratio of 2.04 [0.88, 4.73]. Treatment effects on the primary clinical endpoint of anhedonia symptoms did not significantly differ, with a 14-week estimated difference on the Snaith Hamilton Pleasure Scale (SHAPS) of -0.20 [-2.25, 1.84] points in BATA compared to MBCT (z = 0.19, p = 0.845, d = 0.05). The expected 14-week change in SHAPS scores across conditions was -7.18 [-8.22, -6.15] points (z = 13.6, p <0.001, d = 1.69). There were no significant differences in the proportion of participants demonstrating reliable and clinically significant improvements in SHAPS scores, or in the magnitude of internalizing symptom reductions. Limitations: Limitations included a modest sample size, lack of longer-term follow up data, and non-preregistered analytic plan. Discussion: There was no evidence to support superior clinical efficacy of BATA over MBCT in a transdiagnostic cohort of adults with elevated anhedonia. Both interventions reduced anhedonia symptoms to a comparable magnitude of other existing treatments.