The relationship between perfectionism and treatment outcomes among people receiving internet-based cognitive behaviour therapy for Generalised Anxiety Disorder.

Perfectionism is a transdiagnostic process associated with multiple mental health disorders. Perfectionism can moderate the effectiveness of Cognitive Behavioural Therapy (CBT) for depression, but it remains unclear whether perfectionism is associated with CBT outcomes for anxiety disorders. This study investigated the relationship between perfectionism, treatment outcomes and adherence for individuals seeking internet-based CBT (iCBT) for Generalised Anxiety Disorder (GAD). A total of 1,904 adults from the general Australian community commenced an iCBT GAD program and completed measures of perfectionism, generalised anxiety, depression and psychological distress at baseline, mid-treatment, and post-treatment. Regression analyses were used to examine relationships between baseline perfectionism, post-treatment symptom reductions and treatment completion. Baseline perfectionism was significantly associated with pre-treatment GAD symptom severity, but not treatment completion or reductions in GAD severity post-iCBT. Significant reductions in generalised anxiety symptom severity (Hedges' g = 1.32), depression symptoms (g = 0.97), distress (g = 1.34) and perfectionism (both striving and evaluative concerns, g = 0.49 and g = 0.37, respectively) were observed with treatment. These findings suggest that iCBT for GAD is effective in reducing perfectionism, despite not directly targeting this process. Given there was no significant relationship between baseline perfectionism and treatment outcomes, it may not be necessary to specifically target perfectionism when delivering iCBT for GAD.