There are multiple theories regarding the pathophysiology of depression. The most common (and the one you’ve probably heard about) is the monoamine hypothesis. This theory posits that depression is an imbalance (or depletion) of certain key neurotransmitters in the brain. The imbalance of these key neurotransmitters, namely dopamine, serotonin, and norepinephrine, is believed to cause depression. As such, most common antidepressants fit into classes that limit the uptake and/or breakdown of serotonin (SSRIs), serotonin and norepinephrine (SNRIs and TCAs), or serotonin, norepinephrine, and dopamine (MAOIs).
Today, we’re interested in a different hypothesis involving inflammatory proteins called cytokines. Cytokines are increased within our body when we are having an immune response and with inflammation in general. In patients with depression, certain cytokines have been found to be elevated before treatment (associated with a pro-inflammatory state) and decreased after treatment 1. This implies that cytokines and other inflammatory molecules may cause a pro-inflammatory state that causes our brain to be “inflamed,” thus causing depression. If there were a way to decrease inflammation in our body, perhaps depressive symptoms would improve as well.
On to statins. Statins (think Lipitor, Crestor) are commonly prescribed to treat high cholesterol. Incidentally, they are also believed to have anti-inflammatory properties. This is believed to be the reason why statins decrease the risk for stroke and heart attack independent of their cholesterol lowering effect.
A recent study in Denmark followed 872,216 SSRI users (of whom 113,108 (13.0%) used a statin concomitantly) over the course of 15 years 2. It found that patients who took SSRIs while on a statin had fewer depression-related hospital visits and depression-related hospitalizations. As such, the article concluded that “concomitant treatment with SSRIs and statins resulted in robust advantages compared with SSRIs alone.”
So does this prove the cytokine hypothesis of depression? Should you be taking a statin if you’re depressed? Not quite. Statins are not benign drugs, and the evidence isn’t there yet to recommend augmenting antidepressant treatment with a statin. Regardless, this study represents one more step in the right direction. Here’s to eventually finding a cure (and a satisfying explanation) for the millions of people worldwide who are afflicted with depression.