Effectiveness and mechanisms of internet-delivered transdiagnostic CBT for students with adjustment disorder: the role of cognitive inflexibility, self-compassion, and mindfulness

Adjustment disorder (AjD) is highly prevalent among university students and is associated with significant distress and impaired academic functioning, yet evidence‐based interventions remain limited. This randomized controlled trial evaluated the effectiveness and mechanisms of a six‐week internet‐delivered Unified Protocol (iCBT‐UP) for students with AjD, compared with an active control (iPMR) and a wait‐list control. A total of 181 students meeting ICD‐11 criteria for AjD were randomized (2:2:1) to iCBT‐UP (n = 79), iPMR (n = 63), or wait‐list (n = 39). Assessments were conducted at baseline, post‐treatment, and one‐month follow‐up. Outcomes included AjD, academic adjustment, experiential avoidance, self‐compassion, and mindfulness. Daily diary assessments captured changes in self‐compassion, mindfulness and psychological flexibility. Treatment effects were examined using mixed repeated‐measures ANOVA and mediation analyses. Both active interventions significantly reduced AjD symptoms relative to wait‐list, whereas only iCBT‐UP improved academic adjustment. Reductions in experiential avoidance and increases in self‐compassion mediated the effects of iCBT‐UP on decreases in AjD symptoms. Self‐compassion also mediated the effects of iCBT‐UP on improvements in academic adjustment. Daily diary analyses showed increases in self‐compassion and psychological flexibility in both active conditions. These findings support transdiagnostic CBT as an effective intervention for AjD and highlight key mechanisms of change.