New preliminary findings from a study to be presented at the upcoming American Academy of Neurology’s (AAN) annual meeting suggest that people with depression and anxiety are at a greater risk of developing Alzheimer’s disease at a younger age.

The investigation included 1,500 people with Alzheimer’s disease who were screened for a history of depression, anxiety, bipolar disorder, schizophrenia and posttraumatic stress disorder (PTSD). Overall, participants reported a history of depression (43%), anxiety (32%), bipolar disorder (1.2%), PTSD (1%) and schizophrenia (0.4%).

Scientists noted that in general, individuals with one mental health condition experienced symptoms of dementia almost two years earlier than those without. People with two psychiatric disorders showed symptoms nearly three years earlier than those who had none, and individuals with three or more mental disorders had symptoms about seven years earlier than those without any mental health condition.

Findings also revealed that those with depression and anxiety were primarily female. In keeping with their young age at the onset of dementia, few exhibited common Alzheimer’s risk factors. In addition, people with depression frequently suffered from an autoimmune disease, while those with anxiety showed a history of seizures.

“While this association between depression and autoimmune disease, and seizures and anxiety is quite preliminary, we hypothesize that the presentation of depression in some people could possibly reflect a greater burden of neuroinflammation,” said Zachary A. Miller, MD, an associate professor at the University of California, San Francisco, a member of AAN and the study’s author.

“More research is needed to understand the impact of psychiatric disorders such as depression and anxiety on the development of Alzheimer’s disease and whether treatment and management of depression and anxiety could help prevent or delay the onset of dementia for the people who are susceptible to it,” Miller said.

For related coverage, read “Are Chronic Negative Thoughts a Risk Factor for Dementia?”