Mental health screening in armed forces before the Iraq war and prevention of subsequent psychological morbidity: follow-up study.

OBJECTIVE: To assess whether screening for mental disorder before the start of the 2003 Iraq war would have predicted subsequent mental disorders.
DESIGN: Longitudinal cohort study of the United Kingdom armed forces. PARTICIPANTS: 2820 of 2873 personnel of the three services who completed an initial questionnaire in 2002 were asked to complete a second questionnaire between June 2004 and 2 March 2006.
SETTING: Regiments, air stations, bases, ships, and homes for those who had left the services. MAIN OUTCOME MEASURES: Positive and negative likelihood ratios, and positive and negative predictive value of first assessment compared with assessment two to three years later of post-traumatic stress disorder, general health questionnaire, physical symptoms, self perception of health, and alcohol misuse for the entire group and for those deployed to the Iraq war.
RESULTS: The response rate to the follow-up questionnaire was 69%, adjusted for return to senders. The positive likelihood ratio of post-traumatic stress disorder was high (13.1, 95% confidence interval 7.2 to 23.8), but the negative likelihood ratio was close to 1 (0.78, 0.67 to 0.91). The positive predictive values were low because of the low prevalence of post-traumatic stress disorder in the period before the Iraq war. The positive likelihood ratios for the other psychological assessments varied between 2.7 and 5.6, and the negative likelihood ratios were slightly lower than for post-traumatic stress disorder, indicating that these were not good candidates for screening. Results were the same for the analyses restricted to those who were deployed.
CONCLUSIONS: Screening for common mental disorders before deployment in this cohort would not have reduced subsequent morbidity or predicted post-traumatic stress disorder, but this may change if there is a considerable increase in the prevalence of the disorder.