As someone with family members who struggle with mental illness, I know the stigma that surrounds it: a person who is struggling with depression has some kind of mental and emotional weakness. If they were stronger, better people they could snap out of it.
George Slavich, a clinical psychologist at the University of California in Los Angeles, is one of an increasing number of scientists who believes that we need to be looking at our physiology to better understand depression. Perhaps, it's not all in the head.
"I don't even talk about it as a psychiatric condition any more," he told The Guardian.
Slavich is onto something, as new research shows that many cases of depression are caused by an allergic reaction to inflammation.
Tim de Chant of Nova writes, "Inflammation is our immune system's natural response to injuries, infections or foreign compounds."
Inflammation acts an alert system to the body to close wounds and call other parts of the immune system into action, a family of proteins called cytokines sets off the inflammation in the body, and switches the brain into sickness mode.
Both cytokines and inflammation have been shown to elevate during depressive episodes, and in people with bi-polar, and drop off in periods of remission. Normally, people who don't suffer from depression can be temporarily put into a depressed, anxious state when given a vaccine (like the typhoid vaccine), which causes a spike in inflammation.
If you compare how we feel when we're sick — the listlessness, lack of enthusiasm, troubled sleep, weepy, and a general feeling of wading through tar (or as psychologists call it, sickness behavior with the emotional responses of depression) — they match up pretty well.
There are other signs that inflammation and depression are connected.
People with inflammatory diseases such as rheumatoid arthritis tend to suffer more than average with depression, or cancer patients who are given a drug called interferon alpha, which boosts their inflammatory response to help fight the cancer.
Inflammation is caused by obesity, especially when much of the weight is centered in the stomach area — the belly holds huge amounts of cytokines — a diet rich in trans fats and sugars, and stress, especially the kind that comes from loneliness and social rejection.
Neuroscientist Turhan Canli takes the connection between inflammation and depression even further by suggesting that depression might be an infectious disease caused by a parasite, bacteria, or viral infection. He speaks about his theory in this TED talk below:
But there is good news. A few clinical trials have found adding anti-inflammatory medicines to antidepressants not only improves symptoms, but increases the proportion of people who respond to treatment.
Carmine Pariante, a Kings College psychiatrist quoted in the The Guardian, says that we're between five and ten years away from a blood test that can measure levels of inflammation in depressed people. Meaning, we could potentially in five years have some kind of cure for depression.