Clues say depression may advance aging of brain

Memory and thinking skills naturally slow with age but now scientists are peeking inside living brains to tell if depression might worsen that decline — and finding some worrisome clues. Depression has long been linked to certain cognitive problems, and depression late in life even may be a risk factor for the development of Alzheimer’s. Yet how depression might harm cognition isn’t clear. One possibility

Brain cells communicate by firing messages across connections called synapses. Generally, good cognition is linked to more and stronger synapses. With cognitive impairment, those junctions gradually shrink and die off. But until recently, scientists could count synapses only in brain tissue collected after death.

Yale University scientists used a new technique to scan the brains of living people — and discovered that patients with depression had a lower density of synapses than healthy people the same age.

What it means

The lower the density, the more severe the depression symptoms, particularly problems with attention and loss of interest in previously pleasurable activities, Yale neuroscientist Irina Esterlis said at a meeting of the American Association for the Advancement of Science. She wasn’t studying just seniors but a range of ages including people too young for any cognitive changes to be obvious outside of a brain scan — on the theory that early damage can build up.

“We think depression might be accelerating the normal aging,” she said.

What’s next

To prove if depression really worsens that decline would require tracking synaptic density in larger numbers of people as they get older, to see if and how it fluctuates over time in those with and without depression, cautioned Jovier Evans, a staff scientist at the National Institute on Mental Health.

Esterlis is planning a larger study to do that. It’s delicate research. Volunteers are injected with a radioactive substance that binds to a protein in the vesicles, or storage bins, used by synapses. Then during a PET scan, areas with synapses light up, allowing researchers to see how many are in different regions of the brain. Esterlis said there are no medications that specifically target the underlying synapse damage.

EVAN VUCCI / AP FILE 2015 A nuclear medicine technologist makes a PET scan of a patient at Georgetown University Hospital in Washington. Yale researchers are using PET scans to study key brain connections.