Shorter overseas deployments of U.K. armed forces can help prevent mental illness, say researchers who looked at risks of developing post-traumatic stress disorder, harmful drinking and family problems.

Under the U.K.’s "Harmony Guidelines," the maximum recommended time for operational tours is set at 13 months within a three-year time period. In Tuesday’s online issue of The Lancet Psychiatry, researchers from King’s College estimated how limiting deployments could help prevent mental health problems.

"Extrapolating from our results, a decrease from 22 per cent to 12 per cent in personnel deployed for longer than recommended by the Harmony Guidelines might have prevented 138 cases of PTSD, 453 cases of psychological distress, 309 cases of multiple physical symptoms, and 490 cases of alcohol misuse between November 2004 and September 2009," concluded Roberto Rona, a professor of Public Health Medicine, and the co-authors.

As part of the study, researchers assessed a random sample of 3,982 regular military personnel who had been on overseas tours and asked them to fill in a questionnaire about symptoms of PTSD and other problems. The response rate was 57 per cent, which the authors said is rarely achieved in military studies.

Breaches of the guidelines decreased from 22 per cent in 2005 to 12 per cent in 2008.

The length of deployment is an indicator of the degree of exposure to stressful and traumatic events and points to the amount of non-deployed time available for recovery, professors Robert Ursano, David Benedek and Gary Wynn from the Uniformed Services University School of Medicine in Bethesda, Md., said in a journal commentary published with the study.

"Importantly, number of deployments was not associated with worse mental illness status or problems at home," the commentators said.

But individuals deployed several times are not the same population as those deployed only once, they said, pointing to experience, greater training or involvement in special operations and older age and greater likelihood of being married with children.

Time between deployments important

Dwell time, or the time between deployments for recovery, is an important variable to consider, they said, pointing to a U.S. army finding that suggests units need as much as three years of dwell time to return to baseline rates of mental health.

They added that individuals who respond to public health emergencies, including humanitarian aid and disaster relief, such as after a tsunami or to stop the spread of Ebola, also face stress from deployments.

In the study, deployments were mainly to Afghanistan, Iraq or both, and for a small proportion of the sample, Pakistan, Bosnia, Kosovo or the Persian Gulf.

Last year, a study published in the Canadian Medical Association Journal on Canadian Forces deployment in support of the mission in Afghanistan from 2001 to 2008 concluded that "an important minority," 14 per cent, of personnel had a mental disorder such as PTSD attributed to the deployment.

The U.K. Ministry of Defence funded the study.