(AP) — Scientists are peeking inside living brains to tell if depression might worsen the natural decline in memory and thinking skills as people age — and they are finding some worrisome clues.

Depression has long been linked to certain cognitive problems, and depression late in life may be a risk factor for the development of Alzheimer’s. It’s not clear how.

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But brain cells communicate by firing messages across connections called synapses, and Yale University researchers used a new brain scanning technique to check the levels of people’s synapses. They discovered that patients with mid-life depression had significantly lower synaptic density than healthy people the same age.

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It’s a small study, and doesn’t prove depression was the cause. Researchers next plan to track people over time to measure changes in synapse levels.

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