Is there a link between inflammation and depression?

If you suffer from depression, inflammation in your brain may be contributing to your condition.

A handful of studies suggest that researchers are closing in on a causal relationship between “neuroinflammation” and depression.

The idea of inflammatory causes of depression has existed for a long time — perhaps decades, says Amit Anand, MD, professor and vice chair for research and behavioral health. But interest in this area of research has been growing in recent years. And research has improved in the era of biomarkers, measurable substances in your body that help indicate a disease or process.

Compelling evidence

In one of the most conclusive findings yet, a recent study in JAMA Psychiatry determined that brain inflammation was 30 percent higher in clinically depressed patients. The research team behind the study pointed out that previous studies have looked at biomarkers of inflammation in the blood, but this is the first to find definitive evidence in the brain.

Dr. Anand points to interesting research about the drug interferon, too. Doctors often use interferon to treat hepatitis C, but there’s often a troubling side effect: profound depression.

On the flipside, a 2013 JAMA Psychiatry article found that patients with mild inflammation who took infliximab — a medication used to treat autoimmune or inflammatory diseases — saw decreases in their depression symptoms.

There’s more work to be done, Dr. Anand notes, but the evidence of a link between inflammation and depression is adding up.

Stress is also a factor

Stress may be another part of the equation. Cleveland Clinic researchers have been looking at biomarkers for “blood-brain barrier” disruption or impairment. Sometimes, stress triggers certain proteins that have inflammatory properties to break through the barrier between the brain and the rest of the body.

A Cleveland Clinic study recently determined that children with emotional trauma had higher than normal levels of S100B, a biomarker of blood-brain barrier disruption and brain injury. Another study reported similar findings related to combat training stress in soldiers.

Proteins of this type have also been linked to depression.

In the long term, this link might offer hope for patients. Dr. Anand says new medications need to be developed that could potentially treat these types of impairments and help reverse depression.

Future research for patient solutions

Though the link is growing stronger, Dr. Anand cautions that doctors should not start handing out anti-inflammatory agents just yet.

In most patients, inflammation might just be a contributing factor to depression, as opposed to being the primary cause, he notes. He believes additional research could help solidify a causal relationship between inflammation, stress and depression — and determine whether medication can help.

The ideal, Dr. Anand says, would be to find a biomarker that definitively links inflammation to depression. Then, doctors could use that biomarker to identify at-risk patients.

“Those are the people that you could treat with anti-inflammatory drugs,” he says.

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