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Rosenzweig (1936) noted that diverse psychotherapies often prove similarly successful, leading him to question what common factors make them equally effective.
He referenced the Dodo bird’s quote from Alice’s Adventures in Wonderland, “Everybody has won, and all must have prizes,” and his assertion that different therapies have equivalent outcomes became known as the Dodo bird verdict.
This idea has been empirically supported by research finding few differences between legitimate treatments (e.g., Luborsky et al., 2002; Wampold & Imel, 2015).
Rosenzweig (1936) argued for the importance of common factors in psychotherapy without specifying what they were, only mentioning social reconditioning and catharsis as examples.
While some argue that common factors, such as therapeutic alliance, empathy, and positive regard, are the primary drivers of therapeutic change (Norcross & Lambert, 2019), others emphasize the importance of specific factors, such as particular interventions or techniques.
The complex interplay between common and specific factors, as well as therapist effects and patient characteristics, likely contributes to the effectiveness of psychological therapies.
Specific factors in psychotherapy refer to the unique, theory-driven elements, interventions, or techniques that are believed to be the active ingredients responsible for therapeutic change within a particular treatment approach (Wampold & Imel, 2015).
These factors are often outlined in treatment manuals and are considered distinct from common factors, which are shared across different therapies.
Proponents of specific factors argue that these unique elements are crucial for therapeutic effectiveness and that different psychological disorders require different treatment approaches (Siev, Huppert, & Chambless, 2009).
However, the relative contribution of specific factors compared to common factors in therapeutic change remains a topic of ongoing debate and research in the field of psychotherapy (Laska, Gurman, & Wampold, 2014).
Frank’s common factors model focused on four therapeutic components (Frank, 1961; see also Frank & Frank, 1993):
Wampold and Imel (2015) proposed a contextual model of psychotherapy that includes three pathways:
Like Frank’s model, the emphasis is not on prescribing specific ingredients; what matters is that they are coherent with the treatment’s explanations and rituals and encourage healthy behaviors.
Grencavage and Norcross (1990) conducted a literature review that identified 89 common factors, grouped into five categories: patient characteristics, therapist qualities, change processes, treatment structure, and relationship elements.
Therapist-related factors refer to therapists’ characteristics, actions, and interpersonal variables associated with patient-level outcomes, regardless of the specific therapeutic approach used.
These factors are typically examined through correlational analyses between therapist variables and patient outcomes.
Therapist effects (therapist differences in effectiveness) account for 3-8% of outcome variance. Variables differentiating better-performing therapists include greater facilitative interpersonal skills, professional self-doubt, and deliberate practice.
Common change processes are therapeutic factors believed to facilitate positive outcomes across different therapy approaches.
Treatment structures, such as the virtual healing setting, have received less attention in the psychotherapy literature than other common factors (Grencavage & Norcross, 1990).
However, the COVID-19 pandemic forced many therapists to switch to online therapy, leading to concerns about technical issues and the patient-therapist interaction (Aafjes-van Doorn et al., 2021).
Therapists reported feeling less connected to patients, having difficulty reading emotions, and expressing empathy in online settings.
Although therapists initially felt online therapy was less effective, their views became more positive with experience, highlighting the need for training and research on facilitating relationship factors in internet interventions (Berger, 2017).
An expert panel reviewed meta-analyses and found strong research support for several relationship elements, including alliance, goal consensus, cohesion in group therapy, therapist empathy, and positive regard (Norcross & Lambert, 2019).
The therapeutic alliance is the collaborative and affective bond between therapist and patient. It encompasses agreement on the goals and tasks of therapy and the quality of the emotional bond (Bordin, 1979).
The alliance is considered one of the most important common factors in psychotherapy, and its significance is supported by extensive research evidence.
Several meta-analyses have consistently found that the alliance is a robust predictor of treatment outcomes across various therapeutic approaches and settings, including individual therapy with adults, child/adolescent therapy, and couples and family therapy (Flückiger et al., 2018; Friedlander et al., 2019; Karver et al., 2019).
The alliance remains a significant predictor even when controlling for patients’ intake characteristics and therapists’ adherence and competence (Flückiger, Del Re et al., 2020).
Moreover, research suggests a reciprocal relationship between the alliance and symptom reduction. Improvements in patient-rated alliance quality are associated with subsequent symptom reduction early in therapy, and symptom reduction, in turn, is associated with further improvement in the alliance (Flückiger, Rubel et al., 2020).
The importance of the alliance is further highlighted by research on alliance ruptures and repairs. Alliance ruptures, or tensions and breakdowns in the collaborative relationship between patient and therapist, are common in therapy.
However, evidence suggests that successful rupture repair is a common process that predicts positive treatment outcomes (Eubanks et al., 2019).
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