Preliminary clinical and cost effectiveness of augmented depression therapy versus cognitive behavioural therapy for the treatment of anhedonic depression (ADepT): a single-centre, open-label, parallel-group, pilot, randomised, controlled trial

Background: Anhedonia (reduced interest/pleasure) symptoms and wellbeing deficits are core to depression and predict a poor prognosis. Current depression psychotherapies fail to target these features adequately, contributing to sub-optimal outcomes. Augmented Depression Therapy (ADepT) has been developed to target anhedonia and wellbeing. We aimed to establish clinical and economic proof of concept for ADepT and to examine feasibility of a future definitive trial comparing ADepT to Cognitive Behavioural Therapy (CBT). Methods: In this single-centre, open-label, parallel-group, pilot randomised controlled trial, adults meeting diagnostic criteria for a current major depressive episode, scoring =10 on the Patient Health Questionnaire (PHQ-9) and exhibiting anhedonic features (PHQ-9 item 1 = 2) were recruited primarily from high intensity Improving Access to Psychological Therapy (IAPT) service waiting lists in Devon, UK. Participants were randomised to receive 20 sessions of CBT or ADepT, using a mimimisation algorithm to balance depression severity and antidepressant use between groups. Treatment was delivered in an out-patient university-based specialist mood disorder clinic. Researcher-blinded assessments were completed at intake and six, 12, and 18 months. Co-primary outcomes were depression (PHQ-9) and wellbeing (Warwick Edinburgh Mental Wellbeing Scale) at 6 months. Primary clinical proof-of-concept analyses were intention to treat. Feasibility (including safety) and health economic analyses used complete case data. This trial is registered at the ISRCTN registry, ISRCTN85278228. Findings: Between 3/29/2017 and 7/31/2018, 82 individuals were recruited (102% of target sample) and 41 individuals were allocated to each arm. A minimum adequate treatment dose was completed by 36/41 (88%) of CBT and 35/41 (85%) of ADepT participants. There were two serious adverse events in each arm (primarily suicide attempts; none of which were judged to be trial- or treatment-related), with no other evidence of harms. Intake and six-month primary outcome data was available for 37/41 (90%) CBT participants and 32/41 (78%) ADepT participants. Between-group effects favoured ADepT over CBT for depression (mean? = -1.35, 95% CI = -3.70, 1.00, d = 0.23) and wellbeing (mean? = 2.64, 95% CI = -1.71, 6.99, d = 0.27). At 18 months, the advantage of ADepT over CBT was preserved and ADepT had a >80% probability of cost-effectiveness. Interpretation: These findings provide proof of concept for ADepT and warrant continuation to definitive trial. Funding: NIHR Career Development Fellowship.