The question of what works for whom and why in psychotherapy has preoccupied practitioners since the middle of the last century with the proliferation of models of care, each claiming superiority over all others. What followed were a flood of studies attempting to prove that one or more therapy was preferable, but by 1992, Norcross and Norcross contended that beside the occasional significant finding for a particular therapy, ‘the critical mass of data revealed no difference in effectiveness among the various treatments for psychological distress.’ (Hubble, Duncan, and Miller 1999)
The Common Factors
In 1992 Michael Lambert proposed a different approach which, while not derived from a strictly statistical analysis, incorporated what empirical evidence suggested about psychotherapy. This was the four factors model which was further developed by Duncan, Hubble, and Miller in their book ‘The Heart and Soul of Change.’ Client factors, the strengths and vulnerabilities they bring to therapy and the support or challenges in their world were estimated to account for 40% of outcome variance. Therapist and client relationship variables including caring, empathy, warmth, acceptance, mutual affirmation, encouragement, and risk taking which appear across all theoretical orientations, accounted for 30%. 15% of the outcomes is attributable to the placebo effect and the client’s hope and belief in the process. The final 15% of outcome variance was accounted for by models and technique which include a rationale, explain the client’s difficulties, and provide strategies and procedures. Whatever the explanation all therapies suggest the client ’does something different’.
What is the Current View?
Unsurprisingly Lambert’s model has not been without its critics and there has been significant effort to explore its validity more rigorously. Therapeutic relationship, which includes the bond between client and practitioner, agreement about the goals of therapy and agreement about the tasks of therapy has been viewed as the most important focus of interest. Alliance and outcome have been the subject of a number of studies and often cited as proof for the common factors’ theory. A metanalysis by Horvath et al (2011), based on more than 200 studies, demonstrated that stronger alliances are associated with better outcomes, although the magnitude of the association is modest, with an explained variance in outcome of 7.5%. Cuijpers et al (2019) writing in the Annual Review of Psychology noted that such correlational data cannot be used for causal inferences.
In reviewing the evidence for common factors, these authors conclude ‘To date, research on the working mechanisms and mediators of therapies has always been correlational, and in order to establish that a mediator is indeed a causal factor in the recovery process of a patient, studies must show a temporal relationship between the mediator and an outcome, a dose–response association, evidence that no third variable causes changes in the mediator and the outcome, supportive experimental research, and have a strong theoretical framework. Currently, no common or specific factor meets these criteria and can be considered an empirically validated working mechanism. Therefore, it is still unknown whether therapies work through common or specific factors, or both.’
So, it’s back to the drawing board, but at least practitioners are less focussed on ‘who will win the therapy model race’ and more concerned by what actually works.
Cuijpers,P., Reijnders,M. and Huibers,M. (2019)The Role of Common Factors in Psychotherapy Outcomes Annual Review of Clinical Psychology 15:207–31
