A study involving over 180,000 older veterans (average age 68.8 at study start), of whom 29% had PTSD, has revealed that those with PTSD had a significantly greater risk of developing dementia. Over the seven years of the study, 10.6% of the veterans with PTSD developed dementia compared to 6.6% of those without PTSD. When age was used as the time scale, the risk for those with PTSD was more than double. Results were similar when those with a history of head injury, substance abuse, or clinical depression, were excluded.

One possibility for the link is that the stress induced by PTSD contributes to the development of dementia.