RecruitingBehavioural interventionEffect of Mindfulness-based Neurofeedback for Adolescents With Elevated Repetitive Negative ThinkingThis study will test the hypotheses that adolescent with repetitive negative thinking who at at-risk for serious mental illness will show greater default mode network (DMN) connectivity than healthy controls, at-risk adolescents will show greater changes in DMN connectivity than healthy controls, and that a longer session of mindfulness based neurofeedback will lead to greater reduction in DMN connectivity. To do so, 50 adolescents with elevated repetitive negative thinking and 50 matched healthy control participants will be enrolled into a double-blind randomized clinical trial of a session of mindfulness training with either active mindfulness-basde neurofeedback or sham mindfulness-based neurofeedback.