Definition and Criteria for the Assessment of Expertise in Psychotherapy: Development of the Psychotherapy Expertise Questionnaire (PEQ)

: Therapist expertise is a complex, multifaceted, and continually evolving concept. Defining this construct and its constituent components can yield a substantial contribution to the field of psychotherapy, consequently enhancing the comprehension of the fundamental factors that underlie its effectiveness. Within this framework, the present research aimed at developing and assessing the psychometric properties of the Psychotherapy Expertise Questionnaire (PEQ), a self-report measure to assess therapist expertise. A sample of 260 psychotherapists of various theoretical orientations were involved in this research. They completed a survey that included the PEQ as well as other self-reported measures aimed at evaluating personality traits, self-efficacy, self-esteem, and insight orientation. The analysis provided evidence of a good fit for both a correlational model with eight factors and a higher-order model, where the eight subdimensions were grouped into subjective (performance; cognitive functioning; personal and relational qualities of the therapist; therapist self-assessment) and objective (experience; reputation with clients and colleagues; training and professional updating; deontological ethics and setting rules) factors. The eight dimensions, two higher-order factors, and total score all showed excellent levels of internal consistency. Furthermore, significant associations were found between PEQ scores and insight orientation, general self-efficacy, self-esteem, personality traits, and time exercising clinical practice. To conclude, the Psychotherapy Expertise Questionnaire (PEQ) is a valuable, theoretically guided, and psychometrically robust self-report measure designed to assess therapist expertise and its constitutive dimensions. This measure can have practical applications in guiding tailored training and customised supervision.