Canadian scientists say they’ve made a big breakthrough in depression research with a new study that found inflammation deep in the brains of patients suffering from the illness.

While the research is still in its early stages, it provides scientists with a possible alternative cause for the disease, and an explanation for why between 30 and 50 per cent of patients with depression don’t respond to medication.

Researchers from the Centre for Addiction and Mental Health (CAMH) in Toronto compared the brain scans of 20 patients with clinical depression to the brains scans of 20 people without depression.

They found that those with depression had an average 30 per cent more inflammation in their brains.

And the greater the inflammation, the more severe the patient’s symptoms.

The researchers say their findings are significant, and raise the question of whether getting rid of the inflammation would eliminate depression altogether.

The findings were published Wednesday in the journal JAMA Psychiatry.

Inflammation is the body’s immune response to infection or trauma, and is implicated in a range of illnesses. Statistics show that people with certain inflammatory disease, such as lupus, are several times more likely to develop clinical depression, researcher Dr. Jeffrey Meyer of CAMH told CTV News.

So it’s perhaps not surprising that inflammation is found deep in the brains of patients with clinical depression.

One theory is that patients may have been exposed to an infection or trauma, but their brain has not “cooled off” from the experience, Meyer said.

Neuropsychologist Dr. Margaret McKinnon with St. Joseph's Healthcare said the findings must be replicated in a much larger study to confirm the link between inflammation and depression.

A question that remains, McKinnon says, is “whether the neuro-inflammation occurs before depression or because of it.”

Regardless, because this is the first study to show inflammation inside the brain, “it’s a very important finding,” she said.

Researchers are already starting trials to test whether anti-inflammatory drugs may one day serve as anti-depressants, as well as whether exercise and certain foods can help reduce inflammation.

The research may change how doctors approach depression in just a few years, Meyer said.

“This can be in the three- to five-year range for people to have a new treatment,” he said.

With a report from CTV’s medical specialist Avis Favaro and producer Elizabeth St. Philip