Objectives To establish the level of psychological symptoms and the risk factors for possible decreased mental health among deployed UK maritime forces.

Methods A survey was completed by deployed Royal Navy (RN) personnel which measured the prevalence of common mental disorder (CMD), post-traumatic stress disorder (PTSD) and potential alcohol misuse. Military and operational characteristics were also measured including exposure to potentially traumatic events, problems occurring at home during the deployment, unit cohesion, leadership and morale. Associations between variables of interest were identified using binary logistic regression to generate ORs and 95% CIs adjusted for a range of potential confounding variables.

Results In total, 41.2% (n=572/1387) of respondents reported probable CMD, 7.8% (n=109/1389) probable PTSD and 17.4% (n=242/1387) potentially harmful alcohol use. Lower morale, cohesion, leadership and problems at home were associated with CMD; lower morale, leadership, problems at home and exposure to potentially traumatic events were associated with probable PTSD; working in ships with a smaller crew size was associated with potentially harmful alcohol use.

Conclusions CMD and PTSD were more frequently reported in the maritime environment than during recent land-based deployments. Rates of potentially harmful alcohol use have reduced but remain higher than the wider military. Experiencing problems at home and exposure to potentially traumatic events were associated with experiencing poorer mental health; higher morale, cohesion and better leadership with fewer psychological symptoms.