Inclusion Criteria:  13-18 years old at baseline Mood and Feelings Questionnaire - Childhood, long version (MFQ) score of ≥22 Diagnosis of Major Depressive Disorder by impression from the referring psychiatrist and confirmed using the KSADS Internet access at home Access to a smartphone for personal and private use, with an associated standard data plan (ie. greater than or equal to 500 MB/month) Able to speak and read English fluently  Exclusion Criteria:  Individuals that arecurrently receiving structured psychotherapy Clinically significant suicidal ideation that is defined as 'imminent intent' or attempted suicide in the past 6 months Co-morbid diagnosis of borderline personality disorder (as assessed by the Childhood Interview for Borderline Personality Disorder) (Zanarini, 2003), schizophrenia, bipolar disorder, moderate-to-severe eating disorder, obsessive compulsive disorder and/or severe alcohol/substance use disorder in the past 3 months Youth with known or clinically suspected intellectual disability or autism spectrum disorder Youth who are not able to provide informed consent for any other reason