Acceptance and Commitment Therapy (ACT) Informed Coaching: Examining Outcomes and Mechanisms of Change

This thesis presents a programme of research designed to examine the impact of Acceptance and Commitment Therapy (ACT) informed performance and development coaching. A preliminary repeated measures study tested the impact of a brief ACT-informed coaching intervention on coachee general mental health, generalised self-efficacy, life satisfaction, intrinsic motivation, goal-directed thinking, goal attainment, and psychological flexibility with 53 UK adults. Data were collected at four time points over 5 weeks. Analyses revealed significant increases in general mental health, life satisfaction, goal-directed thinking, and goal attainment. A randomised controlled trial (RCT) study tested the impact of a more substantial ACT-informed coaching intervention on coachee work performance, general mental health, generalised self-efficacy, job satisfaction, job motivation, goaldirected thinking, goal attainment, and psychological flexibility with 126 senior managers in the UK Civil Service. Participants were randomly allocated to either an ACT-informed coaching intervention (n = 65) or a waitlist control condition (n = 61). Data were collected at four time points over 13 weeks. Analyses showed significant increases in general mental health, generalised self-efficacy, goal-directed thinking, goal attainment, and psychological flexibility in the ACT group compared to the control condition. Consistent with ACT theory, analyses indicated that increases in psychological flexibility mediated improvements in general mental health, generalised self-efficacy, goal-directed thinking, and goal attainment. A final parallel mediation study compared the effects of psychological flexibility and working alliance (a plausible alternative mediator) using data from the coaching arm of the RCT study. These analyses revealed that significant increases in psychological flexibility mediated increases in generalised self-efficacy, goal-directed thinking, and goal attainment. Despite significant increases in working alliance over time, no mediation effects for increases in study variables were found. Overall, findings suggest that ACT-informed coaching is an effective approach to performance and development coaching, and psychological flexibility mediates the beneficial impact of the ACT coaching intervention.