It's thought people who've experience post-traumatic stress disorder are twice as likely to develop dementia in later life.
Researchers at University College London found the risk is higher in the general population compared to military veterans.
They suggest that could be down to a better availability of treatment for those leaving warzones.
Mia Maria Gunak, who carried out the research, says there are problems with people accessing support services.
"Often people with PTSD remain untreated for years if they receive treatment at all."
There are several reasons for that, first of all, mental health service capacities and as well as that there's stigmatisation - many people feel guilt and shame. These are things that can be changed so people can receive treatment."