What are the effects of having an illness or injury whilst deployed on post deployment mental health? A population based record linkage study of UK Army personnel who have served in Iraq or Afghanistan

Population based study, linking routinely collected data of attendances at emergency departments in military hospitals in Iraq and Afghanistan [Operational Emergency Department Attendance Register (OpEDAR)], with data on 3896 UK Army personnel who participated in a military health study between 2007 and 2009 and deployed to Iraq or Afghanistan between 2003 to 2009.In total, 13.8% (531/3896) of participants had an event recorded on OpEDAR during deployment; 2.3% (89/3884) were medically evacuated. As expected, those medically evacuated for an injury were at increased risk of post deployment probable PTSD (odds ratio 4.27, 95% confidence interval 1.80-10.12). Less expected was that being medically evacuated for an illness was also associated with a similarly increased risk of probable PTSD (4.39, 1.60-12.07) and common mental disorders (2.79, 1.41-5.51). There was no association between having an OpEDAR event and alcohol misuse. Having an injury caused by hostile action was associated with increased risk of probable PTSD compared to those with a non-hostile injury (3.88, 1.15 to 13.06).Personnel sustaining illnesses on deployment are just as, if not more, at risk of having subsequent mental health problems as personnel who have sustained an injury. Monitoring of mental health problems should consider those with illnesses as well as physical injuries.Routinely collected data suggests around 20% of UK troops attended hospital whilst deployed (on a military operation) in Iraq between 2004 and 2006 [1]. Furthermore, between 2003 and 2009, over 6,900 UK military and civilian personnel were medically evacuated back to the UK from Iraq or Afghanistan [2]. On deployment, personnel can be in combat roles where they are in contact with the opposition or non-combat roles, where contact with the enemy is limited. Historically, a large-proportion of medical casualties and air-evacuations during military operations were related to illness and non-combat injury, particularly diarrho