Systematic review and meta-analysis of transdiagnostic psychological treatments for anxiety and depressive disorders in adulthood.

A broad array of transdiagnostic psychological treatments for depressive and anxiety disorders have been evaluated, but existing reviews of this literature are restricted to face-to-face cognitive behavioural therapy (CBT) protocols. The current meta-analysis focused on studies evaluating clinician-guided internet/computerised or face-to-face manualised transdiagnostic treatments, to examine their effects on anxiety, depression and quality of life (QOL). Results from 50 studies showed that transdiagnostic treatments are efficacious, with large overall mean uncontrolled effects (pre- to post-treatment) for anxiety and depression (gs=.85 and .91 respectively), and medium for QOL (g=.69). Uncontrolled effect sizes were stable at follow-up. Results from 24 RCTs that met inclusion criteria showed that transdiagnostic treatments outperformed control conditions on all outcome measures (controlled ESs: gs=.65, .80, and .46 for anxiety, depression and QOL respectively), with the smallest differences found compared to treatment-as-usual (TAU) control conditions. RCT quality was generally poor, and heterogeneity was high. Examination of the high heterogeneity revealed that CBT protocols were more effective than mindfulness/acceptance protocols for anxiety (uncontrolled ESs: gs=.88 and .61 respectively), but not depression. Treatment delivery format influenced outcomes for anxiety (uncontrolled ESs: group: g=.70, individual: g=.97, computer/internet: g=.96) and depression (uncontrolled ESs: group: g=.89, individual: g=.86, computer/internet: g=.96). Preliminary evidence from 4 comparisons with disorder-specific treatments suggests that transdiagnostic treatments are as effective for reducing anxiety, and may be superior for reducing depression. These findings show that transdiagnostic psychological treatments are efficacious, but higher quality research studies are needed to explore the sources of heterogeneity amongst treatment effects.