A new study from Johns Hopkins Medicine offers a fresh look at how memory loss might be linked to a brain chemical called serotonin—often called the “happiness” chemical.
The findings may help explain why some people develop memory problems before they are officially diagnosed with Alzheimer’s disease.
The study, published in the Journal of Alzheimer’s Disease, focused on people with a condition called mild cognitive impairment (MCI). MCI is a stage between normal aging and Alzheimer’s.
People with MCI often forget things more often, struggle to find words, or even lose their sense of smell. Researchers believe MCI could be an early warning sign of Alzheimer’s.
To learn more, the scientists studied 94 older adults—some with MCI and some without. They used PET scans to look at serotonin levels in the brain. Serotonin helps with mood, sleep, memory, and emotions. When serotonin levels drop, it can lead to depression or anxiety, and now it seems it may also affect memory.
The researchers found that people with MCI had less serotonin activity in key brain areas—up to 25% lower than people without MCI. These areas of the brain are known to help with memory, emotional control, and decision-making. At the same time, the researchers also saw more buildup of amyloid-beta protein, which is linked to Alzheimer’s disease.
Dr. Gwenn Smith, the senior scientist, explained that the drop in serotonin activity seems to be tied to memory problems—even when the usual Alzheimer’s signs, like brain shrinkage or amyloid buildup, were not yet serious. This suggests serotonin might play a unique role in early memory loss.
This study doesn’t prove that low serotonin causes memory loss. But it shows a strong connection. More research is needed to confirm whether increasing serotonin levels could slow or stop the progress from MCI to Alzheimer’s.
The study builds on earlier animal research, where mice lost serotonin function before showing signs of Alzheimer’s. In those animals, lower serotonin was linked to both memory loss and depression. This gives scientists hope that boosting serotonin might help with both memory and mood in people with MCI.
Future studies will follow people with MCI over time to see how serotonin levels change as Alzheimer’s disease progresses. The researchers also plan to test antidepressant medications that work on serotonin to see if they can help protect the brain and memory.
This research opens the door to possible new treatments. If scientists can prove that low serotonin leads to memory loss, then medications that boost serotonin—like some antidepressants—could help keep the brain healthy for longer. It also shows the importance of early brain scans and tests for people who might be at risk of Alzheimer’s.
If you want to keep your brain healthy, recent studies suggest that your diet and daily habits also matter. Eating brain-boosting foods, staying active, and managing stress may also help prevent memory loss. Scientists are even looking into how small lifestyle changes can prevent certain types of dementia.
If you care about Alzheimer’s, please read studies about the likely cause of Alzheimer’s disease , and new non-drug treatment that could help prevent Alzheimer’s.
For more health information, please see recent studies about diet that may help prevent Alzheimer’s, and results showing some dementia cases could be prevented by changing these 12 things.
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