Over the past five years, researchers from around the world have concluded that there is a correlation between chronic inflammation and depression. The inflammation-depression link has been studied by multiple research teams, with findings that may forever change the way doctors treat depression.
Depression has long been thought to be the result of a chemical imbalance in the brain: a lack of the “feel-good” substance called dopamine. However, new research suggests this isn’t the case at all.
What is Inflammation?
Put simply, inflammation is our body’s defense system. There are many types of inflammation, with the two most common being acute inflammation, which causes swelling and redness after an injury, and chronic inflammation, a long-term inflammatory response caused by prolonged infection, injuries, or autoimmune disorders. Inflammation acts as a protective response system, sending “messengers” called cytokines to fight illness and infection. The problem is that this process can be harmful to the surrounding normal tissues.
The connection between depression and inflammation has to do with the brain’s response to inflammation. When the brain is aggravated by infection, trauma, etc., inflammation initiates the release of cytokines, but because there are no immediate, visible symptoms as there are with acute inflammation, it goes unnoticed and becomes chronic.
An article on the link between depression and inflammation cites a study published in the U.S. Library of Medicine stating that this chronic inflammation inside the brain and its tissues is believed to cause depression: “the inflammation inside the brain actually starts eating cells away and disrupting the normal functions.” This type of long-term inflammation in the brain can also cause permanent damage, leading to a host of other conditions such as Alzheimer’s disease.
Findings from Current Studies
Three major studies have come out with findings that support the inflammation-depression connection, with interesting details that may make depression preventable and easier to treat.
- A new study featured by Science Daily and published in Biological Psychiatry provided evidence that inflammation of the hippocampus section of the brain alters its function and contributes to symptoms of depression. This study specifically looked at the correlation of higher instances of depression in patients with multiple sclerosis (MS), finding that the immune response linked to depression could be a shared pathological mechanism that leads to the increased rates of depressive symptoms in patients with MS. The study combined two advanced complementary brain imaging methods to suggest that the inflammation of the hippocampus affects the brain function and causes depression and that this hippocampal inflammation could be the contributing causes of higher rates of depression in MS.
- In one of the largest clinical trials ever conducted in Australia, and the first primary preventative study, researchers studied 16,500 participants over the age of 70. The focus was on the theory that inflammation is a cause of illness, rather than the result. Systematic inflammation is associated with many non-communicative disorders like diabetes and cancer, and depression is usually present or at an increased risk with these disorders. The researchers found that pathways work in both directions. If you have a non-communicative problem which itself generates inflammation, you’re more prone to depression. Researchers also suggest that an anti-inflammatory like aspirin might act as a preventative measure against depression. This is huge since there is currently “no primary preventative pharmo-therapy for depression.”
- A 2016 study out of Japan documented a strong correlation between low blood levels of Omega-3 fatty acids and increased depressive symptoms. The study used blood samples and a 20-question clinical depression survey in a cross-sectional study of 2,123 subjects over the age of 40. The findings showed that subjects with higher levels of Omega-3 in their blood were 43% less likely to develop depression. The conclusion of the study was: Omega-3 compounds have a proven anti-inflammatory effect and may also alleviate depression.
Most researchers in these studies did not suggest anyone stopping anti-depression medication, but with the success rate of antidepressants only around 50%, perhaps supplementing medication with Omega-3 fatty acids and going on a low-inflammation diet can help. Eating foods high in Omega-3 (salmon, cod liver oil, chia seeds, walnuts, etc.) can also help to offset the inflammatory effects of the highly-processed diets of many westerners.
What’s most interesting about this new information is that depression may now be preventable, even through dietary changes and/or an over-the-counter medicine like aspirin.
While many of these studies are very new, what’s obvious is a direct connection between inflammation and depression, both in people suffering from other disorders and in those who are not. It’s an across-the-board finding that may improve the way we treat, and prevent, some mental illness.