The participants were originally part of the European HELIX project.
The new NAMS-led study included more than 2,000 female participants.
Researchers at Columbia University found high blood pressure treatment may reduce the progression of cognitive decline.
"The results of the study underscore the long-term costs of untreated depression and anxiety."
The first study, published in Autism, suggests that siblings of autistic children experience many of the same complications.
It's the first intervention that has been clearly demonstrated to lower the risk of developing memory loss that leads to dementia, researchers say.
"PTSD does appear to increase the risk of hypertension," research has concluded.