Client engagement in psychotherapeutic treatment and associations with client characteristics, therapist characteristics, and treatment factors

• There is a lack of definition and theory for client engagement
• Engagement is a multifaceted process influenced by interrelating client, therapist, and treatment factors
• Clients’ greater capacities to address their problems are associated with engagement
• More than any treatment factor, the therapeutic relationship had the greatest influence on clients’ engagement
• Research is needed to develop a theory for engagement to help practitioners enhance it

Client engagement has been associated with positive psychotherapeutic outcomes, yet it is relatively under-theorized. The aims of this review were to establish how client engagement with psychotherapeutic interventions targeting psychological or behavioral change has been operationally defined and assessed, and the associated client characteristics, therapist characteristic, and treatment factors. Seventy-nine studies were selected for review, revealing inconsistent definitions and assessments of engagement and a broad array of client characteristics and treatment factors investigated. Attendance was frequently used as a proxy for engagement, but may not be reliable. Participation or involvement in conjunction with homework compliance which reflects clients' efforts within and between sessions may more reliably reflect engagement. The findings of associations between client characteristics and engagement variables were equivocal, although clients' capacities to address their problems tended to be positively associated with engagement. Nearly all therapist characteristics, particularly therapists' interpersonal skills, and most treatment factors, particularly strengths-based approaches and the therapeutic relationship, were positively associated with engagement. A theory of engagement that characterizes the function and inter-relations of variables across different psychotherapeutic settings is needed.