Objective: To examine the long-term effects of a stress management intervention (SMI) based on the effort-reward imbalance (ERI) model, on psychological and biological reactions to work stress.
Methods: 174 lower or middle management employees (99% male) were randomly assigned to an intervention or a waiting control group. The programme comprised 24 × 45 min group sessions (2 full days followed by two 4 × 45 min sessions within the next 8 months) on individual work stress situations. The primary endpoint was perceived stress reactivity (Stress Reactivity Scale, SRS), while secondary endpoints were salivary cortisol and α-amylase, anxiety and depression, and ERI. Assessments were repeated in 154 participants 1 year later.
Results: SRS score decreased in both groups. A two-factor ANOVA with repeated measures showed a significant time × group effect (F=5.932; p=0.016) with the greater reduction in the intervention group. For SRS, the effect size (Cohen's d) after 1 year was d=0.416 in the intervention and d=0.166 in the control group. α-Amylase as a measure of sympathetic nervous system activation, decreased more strongly in the intervention group (area under the daytime curve and daytime slope: time × group effect p=0.076 and p=0.075). No difference was observed for cortisol. For depression, anxiety and ERI, improvements were higher in the intervention group but did not reach statistical significance.
Conclusions: SMI based on work stress theory, is effective in reducing perceived stress reactivity and sympathetic activation in lower and middle management employees. Other mental health parameters and ERI show a tendency towards improvement. These beneficial effects are present 1 year later.