People who have experienced post-traumatic stress disorder (PTSD) are up to twice as likely to develop dementia later in life, according to a new study.
Dementia risk among people who have had PTSD was higher in the general population compared to veterans, the research indicates.
Researchers found that in the general population, people with a PTSD diagnosis were more than twice as likely to develop dementia.
They suggest this may point to an effect of treating PTSD, with veterans being more likely to receive treatment for the condition.
The findings also indicate that treating PTSD may reduce subsequent dementia risk.
Researchers analysed the results of 13 studies conducted on four continents – including data from 1,693,678 people – that looked at whether a PTSD diagnosis was associated with increased risk of dementia up to 17 years later.
By pooling data from eight of the studies, the scientists found that people with PTSD faced a 61% higher risk of dementia.
Analysing data from two other studies that used different methods, they found the condition was associated with double the odds of developing dementia.
Senior author Dr Vasiliki Orgeta, from University College London’s Psychiatry division, said: “Our study provides important new evidence of how traumatic experiences can impact brain health, and how the long-term effects of trauma may impact the brain in many ways increasing vulnerability to cognitive decline and dementia.
“A lot of people with PTSD don’t access treatment, sometimes due to a lack of mental health care capacity but also because of stigma which often keeps people away from seeking help.
“We now have more evidence of how traumatic experiences and accessing treatment could have a long-lasting impact for individuals and influence future risk of developing dementia.”
Researchers say the risk could be higher than the studies suggest, as PTSD also increases the likelihood of developing other known dementia risk factors, such as depression, social isolation, or elevated alcohol intake.
These were factors that most of the studies adjusted for.
The study published in the British Journal of Psychiatry suggests it remains unclear how PTSD raises dementia risk.
But the researchers say it may be related to hypervigilance and recurrent re-experiencing of trauma, contributing to threat and stress-related activity in the brain, while withdrawal from social life may reduce cognitive reserve and resilience.
The researchers were supported by the NIHR University College London Hospitals Biomedical Research Centre and the Alzheimer’s Society.