A meta-analysis of common factor and specific treatment effects across theoutcome domains of the phase model of psychotherapy

A meta-analysis was conducted to determine whether the relative magnitude o f common factor and specific treatment effects was related to the classes o f outcome domain (subjective well-being, symptoms, and life functioning) de scribed in Howard, Lueger, Maling, and Martinovitch's 1993 phase model of p sychotherapy. Effect sizes were calculated for 80 outcome studies that each contained no-treatment, common factor, and treatment groups. Contrary to h ypotheses, the magnitude of both (a) common factor versus no-treatment comp arisons (r = .11) and (b) common factor versus specific treatment compariso ns (r = .19) did not differ across domains. The magnitude of both component s of psychotherapy was consistent across a variety of variables. A notable exception was the lack of significant common factor effects in the treatmen t of more revere disorders.