Adjusted total cortical (A), frontal (B), parietal (C), and occipital (D) lobe gray matter (GM) volume plotted as a function of the self-reported frequencies of hearing chemical alarms sound in theater. The y-axis represents the unstandardized residuals that resulted from regressing the regional brain volumes (dependent variables) on age, sex intracranial volume, Kansas-GWI status, predicted Khamasiyah exposure, current PTSD and/or major depressive disorder, current use of psychotropic medication, history of alcohol and/or substance abuse/dependence (independent variables). The square represents the mean value of the unstandardized residuals and the error bars represent the 95% confidence interval.