Background: Research identified psychological characteristics underlying a ‘need for psychological control’ as treatment attrition moderators for anxiety disorders in Cognitive Behavioural Therapy ...Show moreBackground: Research identified psychological characteristics underlying a ‘need for psychological control’ as treatment attrition moderators for anxiety disorders in Cognitive Behavioural Therapy (CBT) and Acceptance and Commitment Therapy (ACT). It has not yet been examined if these characteristics moderate treatment attrition for older adults with anxiety, as this age population experience greater barriers in seeking therapy. Objective: This study evaluated whether the psychological characteristics of experiential avoidance and cognitive reappraisal moderated the observed attrition in CBT, and if mindfulness and positive mental health moderated the observed attrition in ACT. Method: Dutch speaking adults, aged 55-75 (N=314) with mild to moderate anxiety, were randomized into a four session CBT or ACT protocol. In the primary analysis, treatment attrition was defined as attending at least one treatment session but not completing all four sessions. In the secondary analysis, treatment attendance was defined as the total number of completed treatment sessions Results: The observed attrition rates were significantly different between the CBT and ACT condition (ꭓ2=6.58, p=.01). The four psychological characteristics did not significantly predict treatment attrition nor the number of completed treatment sessions in CBT and ACT. Conclusions: This study found no moderation in the examined psychological characteristics on the observed ACT and CBT attrition for older adults with anxiety. These findings may be explained by age related reorientations in the need for control and methodological issues in defining treatment attrition. Methods for developing a multi-layered definition of treatment attrition are discussed, and future directions for treatment attrition moderator research are proposed.Show less