People with Alzheimer’s disease diagnoses may develop symptoms earlier if they have depression, anxiety or a combination of mental health challenges, according to a preliminary study.

Those with depression may start experiencing dementia symptoms about two years earlier than those who do not, reported Zachary A. Miller, M.D., of the University of California, San Francisco. And people with anxiety and Alzheimer’s may show symptoms about three years earlier than those who do not have anxiety, he said.

Beyond depression and anxiety, investigators screened study participants for less common mental health conditions, including bipolar disorder, post-traumatic stress disorder and schizophrenia. In 1,500 participants with Alzheimer’s disease, 43% had a history of depression, and 32% had anxiety, but the other mental health issues were diagnosed in approximately 1% or fewer patients.

But the age of symptom onset decreased twofold with each additional psychiatric disorder diagnosis, Miller and colleagues said. People with three or more psychiatric disorders developed symptoms 7.3 years earlier than those with no such condition, for example.

“Certainly, this isn’t to say that people with depression and anxiety will necessarily develop Alzheimer’s disease, but people with these conditions might consider discussing ways to promote long-term brain health with their healthcare providers,” Miller said.

The next question to be answered is whether treatment and management of depression and anxiety could help prevent or delay the onset of dementia for people who are susceptible to it, he and his colleagues concluded.

The study will be presented at the American Academy of Neurology’s 73rd Annual Meeting in April.