Online acceptance and commitment therapy (iACT) for adults with persistent physical symptoms - 3-month follow-up study of a randomized controlled trial.

Objective: Persistent physical symptoms (PPS) represent a major health problem affecting daily functioning. This RCT aimed to examine whether a guided Internet-based treatment based on acceptance and commitment therapy (ACT) provided additional benefits compared to Treatment as Usual (TAU) in reducing somatic complaints and psychological distress in adults with PPS.

Methods: A total of 103 adults with PPS related to indoor environments, chronic fatigue or both conditions were assigned to receive either either a 14-week intervention (video-based case conceptualization + Internet-based ACT) combined with TAU (iACT + TAU; n = 50) or TAU alone (n = 53). Somatic symptoms, depression, anxiety, insomnia, and psychological flexibility were assessed from pre-intervention to a 3-month follow-up. Additionally, the association between changes in psychological flexibility from pre- to post-intervention and changes in symptoms from pre to 3-month follow-up was explored. Analyses were conducted using a multigroup method with full information maximum likelihood estimator.

Results: The results revealed a significant interaction effect, indicating reductions in somatic symptoms and symptoms of depression and anxiety with moderate to large between-group effects (d = 0.71-1.09). No significant interaction effect was observed in insomnia and measures of psychological flexibility.

Conclusion: Internet-based ACT, when combined with Treatment as Usual, demonstrated efficacy for individuals with PPS associated with indoor environments and chronic fatigue. These findings are pertinent for primary healthcare providers, suggesting that the current treatment model could serve as a low-threshold first-line treatment option.

The Clinical Trial Registration Number: NCT04532827.