Researchers at McGill University and the Douglas Institute learned that two kinds of brain cells work in a different way for people who have depression.
How the Scientists Made the Discovery
They studied brain tissue that had been donated to a special brain bank. This collection is rare because it includes brains from people who had mental‑health conditions.
Using a cutting‑edge method that looks at the DNA and RNA of single cells, they examined thousands of cells from 59 people with depression and 41 people without the illness.
Two Cells That Act Differently
The test showed that a group of excitatory neurons, which help control mood and stress, had unusual gene activity. Another group, a type of microglia that deals with brain inflammation, also showed changes.
When many genes in these cells turn up or down, the cells may not work right, and this could help explain why depression happens.
Why This Matters
The findings give strong evidence that depression is a brain disorder with real, measurable changes, not just feelings.
"Depression is more than emotions; it shows clear changes in the brain," said one of the lead researchers.
What Comes Next
The team wants to see how these cell differences affect the whole brain and whether medicines that target them could help people feel better.
Study Details
The research paper, called "Single‑nucleus chromatin accessibility profiling identifies cell types and functional variants contributing to major depression," was published in Nature Genetics. Funding came from several Canadian health organizations.