Our lab uses a multimodal approach (ecological momentary assessment, passive smartphone sensors and wearables, EEG, fMRI, laboratory-based experiments and clinical interviewing) to investigate the etiology and pathophysiology of depression in adolescents, as well as predictors and mechanisms of change in psychotherapeutic and smartphone-delivered interventions for depressed youth. Ongoing studies are investigating smartphone-based interventions, behavioral activation, mindfulness-based treatments, as well as developing data-driven algorithms to detect heightened negative emotions and to predict depression onset in at-risk youth.