Inflammation is our immune system’s response for fighting off danger in our body, and scientists are beginning to link inflammation to psychological disorders such as depression.
Severe depression affects 6.9 percent of the U.S. population, and more than half of people with major depression are unable to find relief from their symptoms with antidepressants. Interestingly, about a third of depressed patients have consistently high levels of inflammation.
Evidence now suggests that inflammation is more than something simply found in some depressed patients—it could be the cause of their disease. Researchers think the immune system is responsible for this long-term effect due to traumatic events earlier on in life.
In 2012, Duke researchers conducted a study on the connection between inflammation and mood disorders. They looked for the presence of an inflammation marker in the blood called C-reactive protein (CRP). The high amount of CRP led them to believe that childhood emotional distress could lead to the foundation for inflammatory processes in the body.
Duke researchers found the number of cumulative depressive episodes was associated with increased levels of CRP, but they could not definitively say that inflammation caused depression. Rather, the researchers scratched their heads as to whether the presence of depression itself caused inflammation in a chicken-or-the-egg-type scenario.
Now, it’s clearer that the immune system can alter cognitive functioning.
According to Carmine Pariante at King’s College London, “Nearly 30% to 40% of depressed patients have high levels of inflammation, and in these people we think it is part of the causal process.”
An article by the BBC noted Pariante saying, “the evidence supporting this idea is that high levels of inflammation are present even if someone is not depressed, but is at risk of becoming depressed. Adult individuals who have a history of early life trauma, even if they have never been depressed, have an activated immune system so they are in a state of risk.”
But it’s not just the immune biomarker in the blood. There’s something else that’s been found to make the connection.
There is evidence that IL-6, a chemical normally secreted by white blood cells to stimulate an inflammatory immune response to infection or trauma, can affect brain activity in a region called the subgenual cingulate. This region is thought to control mood and anxiety, sleep, memory and self-esteem.
Joseph Hayes at University College London identified a significant link between high levels of a chemical involved in inflammation at age 9, and experiencing aspects of hypomania at age 22.
Additionally, a recent New Scientist article revealed that, high levels of inflammation present in a child could go so far as predicting a higher risk of manic behavior in later life.
Manic behavior can be present in not only bipolar disorder, but also seasonal affective disorder and some forms of psychosis. This is enormous progress for all mood disorders, but especially significant for Bipolar Disorder as the disorder is rarely correctly diagnosed until after a person has a manic episode. Women in particular are “susceptible to misdiagnosis”, and many have to endure many years of untreated mood disorders because of misdiagnosis or lack of treatment.
In the study that solved the chicken-egg connection, PET scans showed significant inflammation in the brains of the people with depression, and the inflammation was most severe among the participants with the most severe depression. People experienced clinical depression exhibited an inflammation increase of 30% in their brains. The study focused specifically on the activation of microglia – immune cells that play a key role in the brain’s response to inflammation.
This new finding could lead to changes being made in the way mood disorders, such as Bipolar Disorder, are treated and how future studies should investigate the possible impact of anti-inflammatory drugs on depression symptoms.
A group called NIMA (Neuroimmunology of Mood Disorders and Alzheimer’s Disease) is currently investigating whether targeting the immune system to fight specific types of inflammation could treat these conditions. They may have a pill to target that specific type of inflammation.
Hopefully, drugs targeting the immune system will provide much needed treatments for patients.
Gallagher, James, Rachael Buchanan, Andrew Luck-Baker. “Depression: A revolution in treatment?”. BBC News. 24 August 2016. Accessed 15 Sep 2016.
Hainer, Ray. “Bipolar Disorder Is Different For Women”. Health: Health Media Ventures, Inc. 01 May 2009. Accessed 10 Sep 2016. http://www.health.com/health/condition-article/0,,20274376,00.html
“Inflammation In Depression: Chicken Or Egg?” Medical News Today. 7 January 2012. Accessed 15 Sep 2016. http://www.medicalnewstoday.com/releases/239994.php
McNamee, David. “Severe depression linked with inflammation in the brain” Medical News Today. 29 January 2015. Accessed 10 Sep 2016.
Nordqvist, Christian. “What Are Antidepressants? How Do Antidepressants Work?”. MNT, MediLexicon Limited. 2014-2016. Web. Accessed 15 Sep. 2016.
Thomson, Helen. “Blood Samples From 9-Year-Olds Can Predict Bipolar Symptoms”. New Scientist. 6 September 2016. Accessed 11 Sep 2016.