Mechanisms of mindfulness-based cognitive therapy in difficult-to-treat depression: moderation and mediation analyses from the RESPOND trial.

Clinical Snapshot

Key Findings

• P Value: Not reported in the abstract

• Effect Size: Not explicitly reported in the abstract; treatment-related increases in decentering partially mediated the effect of MBCT on depressive symptoms at 34-week follow-up

• Primary Outcome: Depressive symptoms measured by PHQ-9 at post-treatment (10 weeks) and follow-up (34 weeks); higher baseline severity predicted greater symptom improvement across both groups

• Nnt Or Sensitivity: NNT not calculable from abstract data; moderated mediation finding indicates the indirect effect of MBCT via decentering was amplified at higher baseline depressive severity, though the magnitude of this moderated indirect effect is not quantified in the abstract

• Confidence Interval: Not reported in the abstract; full SEM estimates with bootstrapped confidence intervals available in the complete manuscript

Clinical Application

MBCT requires trained facilitators and group delivery infrastructure (typically 8-week programmes). Feasibility in routine clinical settings depends on workforce capacity, patient willingness to engage in group-based mindfulness practice, and scheduling. The finding that higher baseline severity does not limit MBCT effectiveness supports offering the intervention to more severely affected patients who might otherwise be excluded. MBCT is not currently listed on the PBS as a standalone funded intervention, but can be delivered within Medicare-funded mental health treatment plans (Mental Health Care Plans, up to 20 sessions per year under GP referral) by appropriately trained psychologists or mental health clinicians. Beyond Blue and the Black Dog Institute support mindfulness-based approaches for depression. The RACGP guidelines for depression management acknowledge psychological therapies including mindfulness-based approaches as evidence-based options. In Australia, DTD is a recognised clinical challenge, and this evidence supports the use of MBCT in patients who have not responded to first-line psychological treatments, including those with more severe ongoing symptoms. Access to MBCT-trained clinicians remains uneven across urban and regional Australia, and telehealth delivery of MBCT groups has been explored as a feasibility solution. TGA considerations are not directly applicable as MBCT is a psychological, not pharmacological, intervention. Adults with difficult-to-treat depression (DTD) who have not achieved remission following high-intensity psychological therapy; applicable to patients with persistent depressive symptoms in secondary and tertiary mental health settings

Abstract

BACKGROUND: Mindfulness-based cognitive therapy (MBCT) was developed for relapse prevention in people with remitted depression but is increasingly used for those with difficult-to-treat depression (DTD). A key question regarding this broader application is whether ongoing depressive symptoms constrain therapeutic responsiveness or disrupt MBCT's proposed mechanism, decentering. We explored whether baseline depressive severity moderates clinical outcomes, whether changes in decentering mediate treatment effects, and whether this mediation varies by baseline severity. METHODS: Secondary moderation, mediation, and moderated mediation analyses were conducted using data from the RESPOND randomized trial (N = 234), comparing MBCT plus treatment as usual (TAU) with TAU alone in adults not remitted after high-intensity psychological therapy. Depressive symptoms (PHQ-9) and decentering (Experiences Questionnaire) were assessed at baseline, post-treatment (10 weeks), and follow-up (34 weeks). Analyses were conducted using structural equation modelling. RESULTS: Higher baseline severity predicted greater symptom improvement across both groups. Treatment-related increases in decentering partially mediated the effect of MBCT on depressive symptoms at follow-up. Although baseline severity did not moderate the treatment effect, it moderated the indirect effect, with decentering more strongly associated with symptom reduction among those with higher baseline depression. Severity did not moderate the acquisition of decentering skills. CONCLUSIONS: Concerns that more severe depressive symptoms limit the effectiveness of MBCT were not supported. MBCT's core mechanism remained operative under substantial symptom burden, with clinical impact amplified at higher severity. These findings reduce key uncertainties regarding the application of MBCT in DTD and support its use across a broad range of symptom severity.

References

1. 1.Barnhofer, T., Dunn, B. D., Strauss, C., Ruths, F. A., Ryan, M., Ladwa, A., Stafford, F., Fichera, R., Metcalfe, I., Young, A. H., & Goldsmith, K. (2026). Mechanisms of mindfulness-based cognitive therapy in difficult-to-treat depression: moderation and mediation analyses from the RESPOND trial. Psychological Medicine. https://doi.org/10.1017/S0033291726105212