Working alliance
The patient-rated therapeutic alliance was assessed via the short (12-item) version of the Working Alliance Inventory [WAI-SR; 24]. It consists of three subscales with four items each rated using a 5-point response scale: (1) agreement on the tasks of treatment, (2) agreement on the goals of treatment and (3) development of an affective bond. The WAI-SR is widely used and has been proven to show good psychometric properties in international as well as German inpatient and outpatient samples [