Practice-based evidence: 45 years of psychotherapy's effectiveness in a private practice

Of 2,259 patients seen during 45 years of private practice, outcome data was produced for 1,599 cases. The mean (SD) number of sessions per case was 18.82 (29.89). The dropout rate was 18.76%. Of all treated cases with outcome data 4 (0.25%) were rated as Much Worse; 11 (0.69%), Worse; 497 (31.08%), No Change from Intake; 546 (34.15%), Improved; and 541 (33.83%), Much Improved. The mean (SD) pre-/post-treatment effect size (ES) was 1.90 (1.61), the median was 1.62, and the range was from -2.91 to +15.22. Patients and parents of minors rated outcomes more positively than the therapist did. Outcome varied significantly across diagnostic categories. There was a significant, positive relationship in length of treatment and outcome. The therapist's effectiveness did not improve across the years. Years with the largest patient caseloads or the greatest proportion of patients with managed-care insurance tended to show the poorest outcomes.