RecruitingBehavioural interventionMechanisms of Behavioral Activation (BA)The investigators will be comparing brain (neural) activation of depressed adolescent patients before, during and after a course of Behavioral Activation (BA) therapy using functional magnetic resonance imaging (fMRI). In particular, the project seeks to determine whether BA targets different neural mechanisms for behavioral avoidance associated with low motivation as compared to threat avoidance. A group of healthy controls will also be scanned as a comparator group for behavioral and imaging measures.