BACKGROUND: In the work and stress literature, surprisingly few studies of stress management interventions have evaluated effects on the perceived psychosocial work environment. Using data from a randomized controlled trial we investigated whether the perceived psychosocial work environment and overcommitment to work improved following a group-based, cognitive-behavioural stress management intervention.

AIMS: We hypothesized that the participants would experience less job demand, overcommitment and effort-reward imbalance (ERI) as well as higher job control following the intervention.

METHODS: Using a wait-list controlled design, 102 participants were randomized to either an intervention group or a wait-list control group. Outcome measures were assessed at baseline and follow-up after three, six and nine months, and analysed using mixed model univariate repeated measures analyses of variance. Results are presented as effect sizes using Cohen's d with confidence intervals (95% CI).

RESULTS: Changes from 0 to 3 months for the intervention group were significantly superior to changes for the wait-list control group on all outcomes. The controlled effect size for job demands was d = 0.42 (0.01-0.84 95% CI), for job control d = 0.39 (0.06-0.71 95% CI), for effort-reward imbalance d = 0.61 (0.22-1.01 95% CI) and for overcommitment d = 0.44 (0.06-0.81 95% CI). Improvements were maintained at three months follow-up after the end of treatment.

CONCLUSIONS: The intervention improved the perceived psychosocial work environment and attitude to work with small-medium effect sizes. To our knowledge, this is the first paper from a randomized controlled trial of a stress-management intervention reporting on these important outcomes.