Participant characteristics.

Introduction
Hospital workers are at high risk for stress-related mental health issues and are considered a vulnerable workforce in most Western countries. Although multilevel interventions that address individual and organizational factors show promise, there is limited robust evidence of their effectiveness in hospital settings. This study evaluated the SEEGEN trial, a cluster-randomized controlled trial conducted in the German healthcare sector, to assess the effectiveness of a structured multilevel intervention designed to reduce psychosocial stress and to promote mental well-being among hospital employees. The intervention included five modules that targeted different hierarchical levels, sources of interpersonal and structural stress, and potentially vulnerable life stages. These modules were: (i) top management training, (ii) dilemma management – coping by taking responsibility, (iii) promoting stress-preventive relational leadership competence, (iv) reconciling work and family life, and (v) staying healthy at work.
Methods
The study was conducted at three clinical centers in Germany and included 18 clusters with a total of N = 415 participants. The clusters were randomly assigned to either an intervention or a wait-list control group. The primary outcome was psychological strain (Irritation Scale; IRR), and the secondary outcomes were mental well-being (WHO-5) and perceived psychosocial safety climate, (PSC-12). Intervention effects were estimated using a two-level linear analysis of covariance. Changes from baseline to the 11-month follow-up were analyzed.
Results
The intervention had no statistically significant effect on the primary or secondary outcomes.
Conclusions
The lack of significant effects may be attributed to low participation rates, an insufficient intervention dosage, and contextual factors, such as the SARS-CoV-2 pandemic and staffing shortages in the participating hospitals. Although the intervention cannot currently be recommended for widespread implementation, the study provides valuable insights into developing, delivering, and overcoming the challenges of multilevel workplace interventions in healthcare settings.