Psychological Mechanisms Running head: PSYCHOLOGICAL MECHANISMS Identifying Psychological Mechanisms Underpinning a Cognitive Behavioural Therapy Intervention for Emotional Burnout

One hundred employees of a UK government department were randomly assigned to one of two conditions: (1) a worksite, group-based, CBT intervention called Acceptance and Commitment Therapy (ACT; n = 43), which aimed to increase participants’ psychological flexibility; and, (2) a waitlist control group (control; n = 57). The ACT group received three half-day sessions of training spread over two and a half months. Data were collected at baseline (T1), at the beginning of the second (T2) and third (T3) workshops, and at six months follow-up (T4). Consistent with ACT theory, analyses revealed that, in comparison to the control group, a significant increase in psychological flexibility from T2 to T3 in the ACT group mediated the subsequent T2 to T4 decrease in emotional exhaustion in the ACT group. Consistent with a theory of emotional burnout development, this significant decrease in emotional exhaustion from T2 to T4 in the ACT group prevented the significant T3 to T4 increase in depersonalization seen in the control group. Strain also decreased from T2 to T3 in the ACT group, only, but no mediator of that improvement was identified. Discussion focuses on implications for theory and practice in the fields of ACT and emotional burnout.