This systematic review assesses the scientific evidence regarding the effectiveness of organisational-level workplace mental health interventions on stress, burnout, non-clinical depressive and anxiety symptoms, and wellbeing in construction workers.

Methods
Eligibility criteria were randomized controlled trials (RCTs), cluster randomized controlled trials (cRCTs), controlled or uncontrolled before- and after studies published in peer-reviewed journals between 2010 and May 2022 in five databases (Academic Search Complete, PsycInfo, PubMed, Scopus and Web of Science). Outcomes were stress, burnout and non-clinical depression and anxiety symptoms, and wellbeing (primary) and workplace changes and sickness absenteeism (secondary). Quality appraisal was conducted using the QATQS scale, a narrative synthesis was applied. The protocol was published in PROSPERO CRD42020183640 https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020183640.

Main results
We identified five articles (four studies) with a total sample size of 260, one cRCT, one controlled before- and after study, and two uncontrolled before- and after studies. The methodological quality of one study was rated as moderate, while for three studies it was weak. One study showed significant effects of a work redesign programme in short-term physiological stress parameters, one study showed a significant employee perceived improvement of information flow after supervisor training and one study showed a substantial non-significant decline in sick leave. There was no significant effect on general mental health (SF12) nor on emotional exhaustion. The focus of all studies was on physical health, while detailed mental health and wellbeing measures were not applied.

Main conclusions
The evidence for the effectiveness of organisational-level workplace mental health interventions in construction workers is limited with opportunities for methodological and conceptual improvement. Recommendations include the use of a wider range of mental health and wellbeing outcomes, interventions tailored to the specific workplace and culture in construction and the application of the principles of complex interventions in design and evaluation.