White DL, Kunik ME, Yu H, et al. - Researchers analyzed veterans using Veterans Administration (VA) health care facilities from October 1, 1999, to September 30, 2013, to ascertain whether traumatic brain injury (TBI) and post‐traumatic stress disorder (PTSD) represent risk factors for Parkinson disease (PD). In this population‐based, matched case‐control study, 176,871 PD cases as well as 707,484 randomly picked PD‐free matched controls were identified. For TBI_mild, TBI_non‐mild, and PTSD, the overall study cohort prevalence was estimated to be 0.65%, 0.69%, and 5.5%, respectively. For the first time ever, an independent link of both TBI and PTSD with increased relative PD risk was revealed in a diverse nationwide cohort of military service veterans. Also, a potential modest synergistic excess risk was suggested for the first time in those with comorbid TBI/PTSD.