Fixed psychotherapy courses are commonly specified before the clinician has observed whether a person is improving rapidly, gradually, or only after an initial delay. The clinical consequences of using early symptom change to select treatment length remain difficult to evaluate in ordinary trials because each participant receives only one duration. This study examined whether a four-session allocation rule could preserve composite recovery while reducing completed sessions relative to fixed 8-, 16-, and 24-session courses. A prespecified Monte Carlo model generated 12,000 synthetic adult outpatient trajectories over 24 sessions. Initial symptom burden, functional impairment, chronicity, clinical complexity, and one of four latent response patterns determined repeated symptom and functioning scores. Logistic models, developed in 6,000 trajectories, estimated the probability of composite recovery by sessions 8 and 16 from initial characteristics and proportional symptom change at session 4. The remaining 6,000 trajectories received an 8-session course when the estimated probability of recovery by session 8 was at least 0.70; otherwise they received 16 sessions when the estimated probability of recovery by session 16 was at least 0.55, and 24 sessions in the remaining cases. Composite recovery required a symptom score of 30 or lower, a symptom reduction of at least 50%, and an 8-point functional gain. Results: The allocation rule achieved 86.0% composite recovery (95% bootstrap interval 85.1–86.8) with a mean of 13.6 sessions (13.5–13.7). Fixed 16 sessions achieved 86.9% recovery (86.0–87.7) with 16.0 sessions, whereas fixed 8 sessions achieved 41.1% recovery (39.9–42.3). The allocation rule assigned 30.1% of participants to 8 sessions, 69.9% to 16 sessions, and 0.02% to 24 sessions. In this synthetic setting, early symptom change can support a shorter average course with recovery close to that of a fixed 16-session schedule. These findings establish operating characteristics of the rule, not clinical effectiveness. Prospective trials should test whether the observed balance between recovery and session use holds in routine care.
Fixed psychotherapy courses are commonly specified before the clinician has observed whether a person is improving rapidly, gradually, or only after an initial delay. The clinical consequences of using early symptom change to select treatment length remain difficult to evaluate in ordinary trials because each participant receives only one duration. This study examined whether a four-session allocation rule could preserve composite recovery while reducing completed sessions relative to fixed 8-, 16-, and 24-session courses. A prespecified Monte Carlo model generated 12,000 synthetic adult outpatient trajectories over 24 sessions. Initial symptom burden, functional impairment, chronicity, clinical complexity, and one of four latent response patterns determined repeated symptom and functioning scores. Logistic models, developed in 6,000 trajectories, estimated the probability of composite recovery by sessions 8 and 16 from initial characteristics and proportional symptom change at session 4. The remaining 6,000 trajectories received an 8-session course when the estimated probability of recovery by session 8 was at least 0.70; otherwise they received 16 sessions when the estimated probability of recovery by session 16 was at least 0.55, and 24 sessions in the remaining cases. Composite recovery required a symptom score of 30 or lower, a symptom reduction of at least 50%, and an 8-point functional gain. Results: The allocation rule achieved 86.0% composite recovery (95% bootstrap interval 85.1–86.8) with a mean of 13.6 sessions (13.5–13.7). Fixed 16 sessions achieved 86.9% recovery (86.0–87.7) with 16.0 sessions, whereas fixed 8 sessions achieved 41.1% recovery (39.9–42.3). The allocation rule assigned 30.1% of participants to 8 sessions, 69.9% to 16 sessions, and 0.02% to 24 sessions. In this synthetic setting, early symptom change can support a shorter average course with recovery close to that of a fixed 16-session schedule. These findings establish operating characteristics of the rule, not clinical effectiveness. Prospective trials should test whether the observed balance between recovery and session use holds in routine care.
