Dataset from Larsson, HArtley and McHugh

The study tested whether a brief web-based Acceptance and Commitment Therapy (ACT) intervention—focusing on contact with the present moment, cognitive defusion, and self-as-context—would improve general mental health among university students compared with a wait-list control group. Secondary hypotheses were that the intervention might reduce depression, anxiety, and stress, and increase psychological flexibility.

Dataset Description

The dataset contains responses from 113 university students (52 intervention, 61 control) who participated in a randomized controlled trial at University College Dublin. Participants were recruited through posters, flyers, and classroom announcements. Eligibility required being over 18, enrolled in higher education, without psychiatric diagnosis or prior ACT/mindfulness training.
• Design: Randomization to either a 3-week ACT intervention (three guided audio exercises, <1 hour total) or a wait-list control.
• Assessments: Pre-treatment, post-treatment, 3-week follow-up.
• Measures:
• General Health Questionnaire (GHQ-12) for overall mental health (primary outcome).
• Depression Anxiety Stress Scales (DASS-21).
• Acceptance and Action Questionnaire (AAQ-2) for psychological inflexibility.

Findings
• General Mental Health (GHQ-12): ACT participants showed a significant reduction in psychological distress at post-treatment compared to controls (p = .005, d = 0.48). At follow-up, effects were maintained but no longer significant (d = 0.34).
• Depression, Anxiety, Stress (DASS-21): No significant between-group effects, though small non-significant improvements occurred within the ACT group.
• Psychological Flexibility (AAQ-2): No significant between-group effects, but within the ACT group experiential avoidance decreased significantly from pre-treatment to follow-up (p = .03, d = 0.59).

Notable Patterns
1. Even with minimal exposure (<1 hour audio), ACT produced short-term improvements in mental health.
2. A large share of participants (58–76%) exceeded clinical cut-offs for distress measures, despite not reporting psychiatric diagnoses—highlighting unmet need and limited help-seeking.
3. Process-level change (psychological flexibility) emerged slowly, suggesting more comprehensive ACT components (e.g., values, committed action) may be necessary for lasting effects.

Interpretation and Use

The data shows that a brief, web-based ACT intervention is feasible and beneficial in the short term, making it a promising low-cost, scalable approach to support student well-being. However, effects faded quickly, underscoring the need for longer or more comprehensive interventions to sustain improvements.

This dataset may be used to:
• Explore moderators of response (e.g., baseline distress).
• Investigate mechanisms of change beyond AAQ-2.
• Compare ACT processes with active controls such as relaxation or behavioral activation.