A prospective study of physical fitness, obesity, and the subsequent risk of mental disorders among healthy young adults in army training

Objective: Mental health disorders contribute substantially to medical and occupational morbidity. The role of fitness and physical activity in the prevention of mental health disorders is not well established, but epidemiologic data suggest that physical activity can protect against anxiety and depression. Method: The analyses presented in this report, from a prospective cohort study, evaluate the association between fitness (as measured by a 5-minute step test), and being overweight (defined as exceeding weight and body fat allowances) at military entrance, with subsequent onset of mental disorder diagnosis in the first year of service. The association between risk factors and mental disorder diagnosis was analyzed using multivariate Poisson regression with the adjusted incidence rate ratio (aIRR) as the measure of association. Results: Among weight-qualified participants, factors associated with increased incidence of mental disorder included failing the physical fitness test (aIRR: 1.36, p < 0.0001), female sex (aIRR: 2.17, p < 0.0001), and smoking (aIRR: 1.49, p < 0.0001). Among fit participants, being overweight was not significantly associated with mental disorder (aIRR: 1.11, p = 0.1540). Conclusions: This test has potential military utility as an adjunct part of the medical examination process. Additional research is needed among civilians to determine if similar associations exist. If so, intervention studies should be conducted to determine if improving physical fitness reduces subsequent psychiatric disorder risk, particularly among young adults entering into stressful situations.