fbpx

Late-Life Mood Disorders May Be Early Alzheimer’s Sign

Sad woman crying behind window, late-life depression linked to Alzheimer’s risk

June 25, 2025

People who develop depression or bipolar disorder later in life may be at increased risk of developing Alzheimer’s disease. A new brain scan study found that people with late-life mood disorders had high brain levels of tau and beta-amyloid, two proteins that are a hallmark of Alzheimer’s disease.

Depression can occur in people with Alzheimer’s disease, exacerbating such symptoms as sadness, apathy, sleep disturbances, and irritability. And depression that recurs throughout adult life is a known risk factor for Alzheimer’s disease.

This study looked at people who developed depression or bipolar disorder later in life, after age 40. Researchers at the National Institutes for Quantum Science and Technology in Japan performed PET brain scans on 52 men and women who had developed late-life mood disorders and compared them with 47 of their peers who did not have mood disorders. None of those studied had serious memory problems or other signs of Alzheimer’s disease.

The results were striking. About 50 percent of those with late-life mood disorders had signs of tau accumulation in their brains, compared to about 15 percent of the healthy controls. Nearly 29 percent of those with mood disorders had beta-amyloid deposits in their brains, compared to only about 2 percent of the healthy controls.

“Because most of the participants with late-life mood disorders in our study had no or mild cognitive decline, these results support the evidence that neurodegenerative diseases, including Alzheimer’s, can initially manifest as psychiatric symptoms,” said study author Dr. Shin Kurose.

The researchers also did follow-up autopsy studies  examining the brains of 208 people who had died, 21 of whom had symptoms of depression or bipolar disorder later in their lives.  They found that those with late life mood disorders had significantly higher signs of tau buildup in their brains than those without such symptoms.  

Many of the autopsy brains from individuals with depression or bipolar disorder showed tau accumulation in the frontal regions of the brain, which is crucial for emotional regulation and cognitive function. The study also revealed that these abnormal proteins could be detected years before traditional cognitive symptoms of dementia appeared. Within the autopsy cases, mood symptoms preceded cognitive symptoms by an average of more than seven years.

The findings, published in the journal Alzheimer’s & Dementia, indicate that depression and other mood symptoms can emerge many years before the typical symptoms of dementia are recognized. They suggest that doctors should consider mood disorders, especially those occurring later in life, as possible early warning signs of Alzheimer’s.

Symptoms of depression include feelings of extreme sadness, apathy, social withdrawal, increased sleepiness or inability to sleep, feelings of worthlessness and thoughts of suicide. Bipolar disorder includes periods of depression that may alternate with manic episodes characterized by irritability, restlessness, heightened energy, racing thoughts, and sleeplessness.

Some people who develop late-life depression or bipolar disorder might benefit from an evaluation for underlying brain changes that may signal an increased risk of developing Alzheimer’s disease. While treatments for Alzheimer’s disease are limited, experts believe that medications may be most effective when given early, before damage to the brain becomes extensive. Early identification of these conditions would allow for earlier intervention with disease-modifying treatments, including some of the newer Alzheimer’s drugs which are most effective at early stages of disease. 

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.  

Source: Shin Kurose, Sho Moriguchi, Manabu Kubota, et al: “Diverse tau pathologies in late-life mood disorders revealed by PET and autopsy assays.” Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, June 9, 2025

Share

Alzheimer's Articles

ALL ARTICLES