NCT03219879.

Methods	Design: RCT Phases: continuation (approximately 26 weeks) Comparison groups: T‐CT (telephone‐delivered cognitive‐behavioral continuation therapy) vs usual care Funded by: University of Zurich
Participants	Estimated enrolment: 218 Ages: 18 years to 75 years Sexes Eligible for Study: All Diagnoses: Recurrent major depressive disorder or chronic/persistent depressive disorder based on the criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM‐5)
Interventions	Continuation treatment (approximately 26 weeks) Behavioral: telephone‐administered continuation therapy The intervention includes eight therapy sessions of approximately 50 minutes duration delivered over the telephone by trained psychotherapists over a time period of six months. The intervention is grounded in the principles of psychological continuation therapy and relapse prevention, and includes strategies such as transferring helpful elements of acute‐phase cognitive‐behavioral therapy for depression to daily life. T‐CT is offered in addition to usual care. Other: Usual care Usual care without any study‐related intervention Other Name: Treatment as usual
Outcomes	Primary outcome: Relapse of a major depressive episode (time frame: 6 months, 12 months, and 18 months after baseline) Secondary outcomes: Well‐weeks (time frame: 6 months, 12 months, and 18 months after baseline) Depressive symptoms (time frame: baseline, 3 months, 6 months, and 12 months after baseline) Health‐related quality of life (time frame: baseline, 3 months, 6 months, and 12 months after baseline) Anxiety symptoms (time frame: baseline, 3 months, 6 months, and 12 months after baseline) Psychosocial functioning (time frame: 6 months and 12 months after baseline) Cost of health care utilization (time frame: baseline, 6 months, and 12 months after baseline) Cost‐effectiveness (time frame: baseline, 6 months, and 12 months after baseline) Other Pre‐specified Outcome Measures: T‐CT acceptability (time frame: 6 months after baseline) Treatment satisfaction (time frame: baseline, and 6 months after baseline) Self‐confidence (time frame: baseline, 6 months, and 12 months after baseline) Physical activity (time frame: baseline, 6 months, and 12 months after baseline) Self‐efficacy for depression self‐management (time frame: baseline, 3 months, 6 months, and 12 months after baseline) Self‐management behaviours (time frame: baseline, 3 months, 6 months, and 12 months after baseline) Interpersonal emotion regulation skills (time frame: baseline, 6 months, and 12 months after baseline) Therapeutic alliance (time frame: baseline, 3 months, and 6 months after baseline)
Notes

DSM‐5: Diagnostic and Statistical Manual of Mental Disorders 5th Edition; RCT: randomized controlled trial; T‐CT: telephone‐delivered cognitive‐behavioral continuation therapy