Mental health screening before troop deployment

The United Kingdom and United States have a long history of trying to identify mental health problems among troops to be deployed. Since the first world war, a series of psychological screening programmes have been implemented, but none has been successful in providing a more capable combat force.¹ Nevertheless, there is an understandable interest in developing new screening strategies to reduce the psychological morbidity of troops currently serving in Iraq and Afghanistan.² In this week's issue, Rona and colleagues report the effects of screening troops for mental health problems before deployment to Iraq.³

Two major approaches to predeployment screening exist. The first is to identify troops who are already experiencing debilitating medical and psychological illnesses just before deployment. The advantages of not sending sick troops into a conflict are obvious. These screening programmes are therefore useful, provided they accurately identify troops who need health care, are cost effective, and do not hinder demanding deployment preparations. The second is to identify soldiers who are considered healthy but who have a “propensity” to break down in battle or develop chronic psychological problems.

The study by Rona and colleagues evaluates the second approach and finds that a screening questionnaire administered to troops before deployment to Iraq was possibly useful for identifying post-traumatic stress disorder but not for other mental disorders.³ The marginal benefit was partly because the frequency of mental health problems was low among these troops, which is a common problem in screening generally healthy military populations.

The UK and US military already use a rigorous selection strategy that greatly reduces predeployment morbidity. This process begins with high induction standards, which ensure that most recruits are physically healthy and can complete a basic education. Qualified recruits then undergo basic training, which severely tests physical and mental abilities. Although exceptions exist, important health problems become obvious to drill instructors during the rigours of basic training and result in early discharge.

Newly trained troops usually do not head directly to war, so the military has the opportunity to assess mental fitness further. Troops have to prove that they can cooperate in team efforts and perform complex tasks in confusing circumstances. In contrast to actively serving troops, reserve and National Guard personnel are not observed daily, but they still have to complete basic training, after which they typically serve on active duty for several years and then engage in periodic training exercises.

When troops reach the battlefield, this multilayered selection process has already produced a combat force with a high level of mental and physical health. The effectiveness of this process has been clearly demonstrated and labelled the “healthy warrior effect.” Veterans of the first Gulf war provide a good example of how military service successfully produces fit combat troops. Since 1991, the mortality rate of 700 000 US Gulf war veterans has been less than half that of the civilian population.⁴ British veterans of the Gulf war have also had favourable mortality rates despite wartime trauma.⁵

For predeployment screening to be justified, it must identify troops who have disqualifying conditions, but who have not already been eliminated by a lengthy process that selects healthy troops. Consequently, it has been difficult to show that mental health screening adds value. The usual benefits of health screening are less apparent in young combat troops than in the general population, which has greater unmet medical and social needs.

The second approach to predeployment screening, which identifies troops who are not having mental health problems but who are more likely to break down in battle or develop chronic psychological problems, is more controversial. Since the first world war, such efforts have been unable accurately to identify individual soldiers who will develop mental disorders.¹ However, based on factors like educational level and rank, they have identified military populations at higher risk of psychiatric breakdown. But even within these at risk populations, most soldiers perform as well in combat as others.^{6 7}

Predeployment screening is intended to reduce psychological morbidity and improve combat effectiveness by identifying vulnerable people and categorising them as unfit for military duty. An unavoidable side effect of this screening approach, however, has been that many people have been inaccurately classified as being psychologically impaired. What effect this has had on their self perception and subsequent lives is unknown, but the military definitely lost a substantial proportion of its workforce.⁸

Because screening has repeatedly failed to predict psychological vulnerability, other health measures should be emphasised, such as increased access to health care and elimination of the stigma associated with treatment for psychological conditions.² Moreover, no comparable screening programme in non-military populations supports this approach. Because of the complexity of human nature, human behaviour has not been consistently predicted in any walk of life, let alone on the battlefield.