Mindfulness-Based Cognitive Therapy (MBCT) is an efficacious treatment for patients with symptoms of depression. However, the processes by which MBCT achieves its outcomes are not well understood. Drawing on literature on basic cognitive functioning and cognitive biases in depression, this K23 will use a randomized controlled trial to test the effect of MBCT vs. Health Education (HE) on affective inhibition (an important component of executive functioning (EF)), and a possible mechanism of action by which MBCT has an impact on depression symptoms. As a secondary aim, this project will also test the effect of MBCT vs. HE on affective updating and affective shifting (two remaining components of EF). In exploratory analyses, we will examine whether depression symptom severity covaries with change in affective EF (i.e., affective inhibition, shifting, and updating) overtime, and whether adherence to the treatment protocol predicts endpoint EF. To accomplish these goals, 76 adult participants with elevated depression symptoms will be recruited from the community and will be randomized to either an 8-week MBCT course at the Mindfulness Center at Brown University or an 8-week Psychoeducational Health Education Class (i.e., a control arm). Participants will complete validated computer-based tasks of affective EF at 5-assessments, 2 before, 2 during, and 1 after, the 8-week MBCT or HE programs. This project directly addresses NCCIH’s objective to advance the understanding of mechanisms through which mind and body approaches affect health, resilience and well-being. This project will directly address the candidate’s training goals of gaining clinical trials methods experience with mood disorders, expanding knowledge of mindfulness-based interventions (specifically MBCT), gain knowledge in neurocognitive assessment of individuals with depression symptoms, receive training in repeated longitudinal assessment, and further develop professional development, research ethics, and grants management skills. The candidate will complete a number of formal and informal activities (e.g., courses, workshops, conferences, directed readings, and regularly scheduled meetings with mentors) to meet the training goals. These training goals will assist the candidate to become a successful independent investigator examining cognitive mechanisms of mind-body interventions for depression and related disorders. The Mindfulness Center at Brown University and Butler Hospital are the ideal environments for this project, as they are leading institutions in clinical trials research and mindfulness-based interventions, with numerous opportunities for training and support services embedded within the systems.