LAUSR

Background There is emerging recognition of the important co-morbidities and long term relationships between physical and psychological health in military and veteran populations. The aim was to investigate the longitudinal relationships between multisymptom illness (MSI) and psychological disorders. Methods A cohort of 1990–1991 Gulf War veterans and military comparison group was assessed at Wave 1 (2000–2002) and Wave 2 (2011–2012), including military service characteristics, symptoms, modified Centers for Disease Control (CDC) definition of MSI, the posttraumatic stress disorder (PTSD) Checklist (PCL), and Alcohol Use Disorder Identification Test (AUDIT). The Composite International Diagnostic Interview (CIDI v.2.1) assessed psychological disorders using DSM-IV criteria. Incident cases were defined as participants who did not meet criteria for a health outcome at Wave 1 but met these criteria at Wave 2. Results Overall participation at Wave 2 was 1390/2779 (50.0%); 99.8% completed a health questionnaire including 1356 male participants who were included in these analyses. The adjusted incident rate ratio (IRR) of MSI at Wave 2 was higher for those with, compared to those without, CIDI-defined PTSD IRR 3.3 (95% CI 1.8–6.0), major depression 2.1 (1.3–3.5) and alcohol disorder 1.8 (1.0–3.3) at Wave 1. The adjusted IRR of incident CIDI-defined PTSD 3.7 (2.2–6.3) major depression 2.0 (1.2–3.2) and AUD 2.1 (1.1–3.8) at Wave 2 were increased for those with, compared to those without, MSI at Wave 1. Conclusions Longitudinally, psychological disorders, in particular PTSD and depression, were found to be a risk factor for the development of MSI and the presence of MSI was a risk factor for the development of psychological disorders, in particular PTSD and depression. These findings have important implications for clinical and occupational health practice, service provision and longer term health in military and veteran populations.