Psychosocial treatments for employees with non-specific and persistent physical symptoms associated with indoor air: A randomised controlled trial with a one-year follow-up

Objective: Persistent physical symptoms (PPS) associated with indoor air without an adequate pathophysiological- or environmental-related explanation may lead to work disability and decreased health-related quality of life (HRQoL). We attempted to assess the effect of cognitive behavioural therapy (CBT) for PPS and also psychoeducation (PE) on these symptoms involving disability. Method: The intention-to-treat (ITT) sample included 52 employees recruited from an occupational healthcare service randomised as either controls undergoing treatment as usual (TAU) or TAU enhanced with CBT or PE. The primary outcome was HRQoL measuring the severity of symptoms and restrictions in everyday life caused by them. Secondary outcomes included depressive, anxiety and insomnia symptoms, and intolerance to environmental factors, assessed at baseline and at 3-, 6- and 12-month follow-ups. Results: At the 12-month follow-up assessment point, no statistically significant differences between treatments emerged following adjustment for gender, age, and HRQoL before the waiting period in the ITT analysis [F(2,46) = 2.89, p=.07]. The secondary analysis revealed a significant improvement in HRQoL in the combined intervention group as compared with controls [F(1,47) = 5.06, p = .03, g = 0.41]. In total, 15% of participants dropped out during follow-up. Conclusions: The results suggest that CBT for PPS or PE might not have a robust effect on HRQoL in PPS associated with indoor air, but the study did not achieve the planned power. Despite difficulties during the recruitment process, the final dropout rates remained low, and participants positively evaluated CBT, suggesting that it represents an acceptable treatment to them.