BackgroundDepression is a widespread disorder with severe impacts for individuals and society, especially in its chronic form. Current treatment approaches for persistent depression have focused primarily on reducing negative affect and have paid little attention to promoting positive affect. Previous studies have shown that metta meditation increases positive affect in chronically depressed patients. Results from previous trials provide evidence for the efficacy of a stand-alone metta meditation group treatment in combination with mindfulness-based approaches. Further research is needed to better understand the implementation of meditation practice into everyday life. Therefore, mindfulness and metta meditation in a group setting are combined with individual cognitive behavioral therapy (CBT) into a new, low-intensity, cost-effective treatment (“MeCBT”) for chronic depression.Methods/designIn this single-center, randomized, observer-blinded, parallel-group clinical trial we will test the efficacy of MeCBT in reducing depression compared to a wait-list control condition. Forty-eight participants in a balanced design will be allocated randomly to a treatment group or a wait-list control group. Metta-based group meditation will be offered in eight weekly sessions and one additional half-day retreat. Subsequent individual CBT will be conducted in eight fortnightly sessions. Outcome measures will be assessed at four time points: before intervention (T0); after group meditation (T1); after individual CBT (T2); and, in the treated group only, at 6-month follow-up (T3). Changes in depressive symptoms (clinician rating), assessed with the Quick Inventory of Depressive Symptoms (QIDS-C) are the primary outcome. We expect a significant decline of depressive symptoms at T2 compared to the wait-list control group. Secondary outcome measures include self-rated depression, mindfulness, benevolence, rumination, emotion regulation, social connectedness, social functioning, as well as behavioral and cognitive avoidance. We will explore changes at T1 and T2 in all these secondary outcome variables.DiscussionTo our knowledge this is the first study to combine a group program focusing on Metta meditation with state-of-the art individual CBT specifically tailored to chronic depression. Implications for further refinement and examination of the treatment program are discussed.Trial registrationISRCTN, ISRCTN97264476. Registered 29 March 2018 (applied on 14 December 2017)—retrospectively registered.