The UK armed forces have recommended deployment levels called the harmony guidelines, reflecting the need to balance rest and recuperation with deployment. In times of simultaneous major operations, such as those in Iraq and Afganistan, this tool is helpful for monitoring overstretch as a measure of over-commitment.
So a study carried by Professor Roberto Rona and colleagues at King's College London, set out to assess whether deployments above these guidelines (calculated as 13 months or more in a three year period) have an effect on psychological health.
They studied the number and duration of deployments in the last three years of a random sample of 5,547 regular military personnel. Mental health and alcohol use were assessed using recognised scoring methods.
Other outcomes included intentions to stay in the military and problems at home during and after deployment. All analyses were adjusted for factors such as age, gender, rank, marital status and Service. Further adjustments were made for role in theatre (combat or support), type of deployment (war or peace enforcement operations), and time spent in a forward area in close contact with the enemy.
They found that those who were deployed for 13 months or more over a three year period were more likely to have symptoms of post traumatic stress disorder and problems at home during and after deployment. This was particularly apparent in those with direct combat exposure. The prevalence of severe alcohol problems also increased with longer deployment.
There was no association between duration of deployment and intention to stay in the military. The relation between number of deployments and psychological symptoms was less consistent and there was no link between number of deployments and problems at home.
There was a moderately strong association between post traumatic stress disorder and a longer than expected period of deployment for the most recent deployment. This is consistent with a survey of US troops in Iraq, which found that an uncertain date of returning home increased psychological distress.
These results suggest that deployment above the recommended limit (overstretch) in the UK armed forces is associated with poor mental health and problems at home, say the authors. This may be more apparent in those with direct combat exposure.
They call for a clear and explicit policy on the duration of each deployment to help reduce the risk of post traumatic stress disorder.