To manualize, or not to manualize: Is that still the question? A systematic review of empirical evidence for manual superiority in psychological treatment.

OBJECTIVE: Institutional promotion of psychotherapy manuals as a requirement for evidence-based treatments (EBTs) yields the assumption that manualized treatment is more effective than nonmanualized treatment. This systematic review examines empirical evidence for this claim. METHODS: An electronic database search identified studies that directly or indirectly compared manual-based and non-manual-based treatment. RESULTS: Six studies directly compared manualized and nonmanualized treatment (Hypothesis 1). None support manual superiority. Eight meta-analyses indirectly assessed effect sizes of manual-based treatment and control groups (Hypothesis 2). Three support manual superiority, five do not. One meta-analysis and 15 further studies addressed manual adherence as an indirect indicator of manual efficacy (Hypothesis 3). The meta-analysis concluded that manual adherence does not affect outcome, additional studies provided inconclusive results. CONCLUSIONS: Manualized treatment is not empirically supported as more effective than nonmanualized treatment. While manual-based treatment may be attractive as a research tool, it should not be promoted as being superior to nonmanualized psychotherapy for clinical practice.