In a new study, researchers found that having depression is known to increase your risk for developing Alzheimer’s disease.
They found that if people do develop Alzheimer’s disease, those with depression may start having dementia symptoms about two years earlier than those who do not have depression.
People with anxiety who develop Alzheimer’s may start experiencing dementia symptoms about three years earlier than those who do not have anxiety.
The research was conducted by a team at the University of California, San Francisco.
Beyond the most common psychiatric disorders, depression and anxiety, the study also screened for a history of bipolar disorder, post-traumatic stress disorder, and schizophrenia.
Of the 1,500 people in the study with Alzheimer’s disease, 43% had a history of depression, 32% had anxiety, 1.2% bipolar disorder, 1% post-traumatic stress disorder and 0.4% schizophrenia.
Researchers also found a serial decrease in the age when symptoms first started that doubled with each additional psychiatric disorder diagnosis.
People with only one disorder developed symptoms about 1.5 years before those with no psychiatric disorders.
Those with two psychiatric conditions developed symptoms 3.3 years earlier than those with no conditions.
And those with three or more psychiatric disorders developed symptoms 7.3 years earlier than those with no such conditions.
In addition to screening for a history of any of these five psychiatric disorders, researchers also looked at the interactions between psychiatric disease and other well-established risk factors for Alzheimer’s disease.
The risk factors include high blood pressure, high cholesterol and diabetes, along with factors that have more recently been linked to an increased risk for Alzheimer’s disease, such as having an autoimmune disease or a history of seizures.
The researchers found that people with depression and anxiety were more likely to be female and consistent with their younger age at onset, had fewer of the typical Alzheimer’s risk factors. However, those with depression were more likely to also have an autoimmune disease and those with anxiety were more likely to have a history of seizures.
The researchers hypothesize that depression in some people could possibly reflect a greater burden of neuroinflammation.
Anxiety might indicate a greater degree of neuronal hyperexcitability, where the networks in the brain are overstimulated, potentially opening up new therapeutic targets for dementia prevention.
One author of the study is Zachary A. Miller, M.D.
The study was presented at the American Academy of Neurology’s 73rd Annual Meeting.
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