Modeling psychotherapy outcome as event in time: an application of multistate analysis

Standard survival analysis (SA) and multistate analysis (MSA) are methods for modeling categorical psychotherapy outcome events over time. The underlying principles, mathematical details, and indications for using each technique are discussed, and data from an anorexia nervosa psychotherapy outcome study comparing psychodynamic psychotherapy with psychodynamic psychotherapy plus cognitive-behavioral techniques are used to illustrate the use of SA and MSA techniques. MSA includes multiple competing outcome states in a single model. A single MSA model includes reaching target weight and treatment dropout before reaching target weight as competing events. It is concluded that MSA is an informative analytic technique in the domain of psychotherapy research.