Professional Psychology: Research and Practice, Vol 57(1), Feb 2026, 12-18; doi:10.1037/pro0000660
This integrative review examines five enduring controversies in psychotherapy—early change, sudden gains, the dose–effect relationship, the effectiveness of brief therapy, and the comparable efficacy of paraprofessionals versus professionals. Despite extensive research, these phenomena remain theoretically underexplained. This review describes these five areas, summarizes their common features in terms of a process/outcome model, and provides a summary and implications. Empirical findings suggest that common factors, particularly the working alliance, can produce early progress reflected in reductions in state negative affect (NA), a global construct encompassing symptoms including depression, anxiety, and psychological distress. Psychometric analyses support this interpretation as widely used outcome measures predominantly assess NA. Recognizing NA reduction as the primary short-term outcome in psychotherapy offers a unifying explanation for multiple phenomena and promotes transdiagnostic, transtheoretical treatment approaches for short-term interventions. Focusing on common factors in early sessions, targeting outcome measurement on NA, and designing flexible, individualized treatment plans that acknowledge variability in clients’ early responses to therapy will decrease client attrition and enhance client engagement to participate in longer term psychosocial interventions. (PsycInfo Database Record (c) 2026 APA, all rights reserved)