Daria Mousavi, Winfried Rief, Marcel Wilhelm
Procrastination is highly prevalent among university students and associated with substantial impairments in well-being and functioning. This randomized controlled trial examined the efficacy of two single-session interventions (SSIs) - one based on Cognitive Behavioural Therapy (CBT) and one on Acceptance and Commitment Therapy (ACT) - for reducing procrastination and tested the role of outcome expectations and experimentally induced expectation (in)congruence. A total of 151 students with recurrent procrastination and a currently postponed task were randomly assigned to a CBT-SSI, ACT-SSI, or a no-intervention control group. Interventions (approximately 60 minutes) were delivered face-to-face and preceded by a videotaped ACT- or CBT-based treatment rationale to manipulate expectation congruence. Assessments took place at baseline, post-intervention, and 2-week follow-up. The primary outcome was state procrastination (APSI-d); secondary outcomes included APSI-d Anxiety and Doubt and Task Aversion, depressive symptoms (PHQ-9), psychological flexibility (CompACT-8), perceived improvement and improvement expectations (G-EEE). Linear mixed models showed a substantial time x condition interaction for state procrastination, with both SSIs yielding significantly greater reductions than the control group and no significant difference between CBT and ACT. Similar patterns emerged for task-related anxiety and doubt, depressive symptoms, psychological flexibility (small-to-moderate gains), and perceived improvement. Higher baseline improvement expectations were associated with greater improvement, whereas expectation congruence and experimentally induced expectation violation did not differentially affect expectations or outcomes. Findings suggest that CBT- and ACT-based SSIs are effective, low-threshold options for reducing procrastination in students in the short term and highlight adherence and treatment expectations as important levers for optimizing brief interventions.