Inclusion Criteria:  Primary DSM-5 diagnosis of PDD (300.4, 296.2x, 296.3x) Total Hamilton Depression Rating Scale (HDRS-24) Score ≥ 20 Treatment-resistance (TR) (defined as a level of 3 or higher on the Antidepressant Treatment History Form: Short Form (ATHF-SF) or medication intolerance or one psychotherapy at least 25 sessions by a certified therapist in the current episode) Sufficient knowledge of the German language Written informed consent  Exclusion Criteria:  Bipolar I or II disorder Active substance use disorders (abstinence shorter than 6 months) Schizophrenia spectrum and other psychotic disorders Antisocial personality disorder Acute suicidality Previous CBASP or BA treatment within the last year Inability to tolerate CBASP or BA (e.g., organic brain disorders, severe cognitive deficits) Inability to participate in dayclinic or outpatient continuation treatment