Understandably, over the last few days there's been a lot of coverage in the UK TV of the First World War. I was struck by the similarity in the symptoms between "shell shock" (now named PTSD) and Parkinson's.

Using data from Taiwan, Chan et al. estimate that patients with PTSD have a hazard ratio of 3.46 of developing PD [1]. (Behind a paywall.)

Reference:

[1] "Post-traumatic Stress Disorder and Risk of Parkinson Disease: A Nationwide Longitudinal Study."
Chan et al.
Am J Geriatr Psychiatry, March 2017
Post-traumatic Stress Disorder and Risk of Parkinson Disease: A Nationwide Longitudinal Study. - PubMed - NCBI

John