An ongoing study is finding that there may be a connection between depression and inflammation in the peripheral blood and the brain.
“People who have depression have a much higher level of something called interleukin, or IL6,” Yvette Sheline, head of the Center for Neuromodulation in Depression and Stress at the University of Pennsylvania, said. “This factor, this cytokine is associated with decreases in cognitive performance and increases in the risk for depression.”
IL6 is a cytokine that is produced naturally in the body to fight off infection. Having too much of it causes depression because it degrades serotonin, a chemical regarded by some researchers as responsible for maintaining mood balance.
“In animal models, when you expose the animal to [IL6] chronically, they get depressed,” Sheline said. “With humans, if you induce this artificially with interferon, which is a treatment for cancer, then about a quarter of the people who’ve never had depression before get depressed.”
They noticed that people with late-life depression are harder to treat. That’s because as we age, we start to produce more of these cytokines.
“So it’s like you get a double whammy. You’ve got aging and you’ve got depression, and so the likelihood is that you may have a treatable inflammation that we could treat along with depression and get you a better treatment response,” Sheline said.
However, Sheline says we need to take a couple more steps before treatment is made available. First, there needs to be proof that there is a causal link between inflammation and depression. No one has ever proven that, but Sheline is hoping their study will.
“Our study, when we finish it, will be the first to actually measure cytokines in the spinal fluid that bathes the brain to see what the levels are. Then we’ll see if the people who get well are the people who have lower levels and the people who have a more difficult time getting a treatment response are the people who have higher levels,” she said.
The next step is adding in an anti-inflammatory agent with the antidepressant.
“People will first get treated with an antidepressant and we’ll see if that lowers the amount of inflammation they have and lowers their depression,” Sheline said. “Then in the second step, we’ll add in an anti-inflammatory agent and see if that gives them an improved treatment response.”