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Chronic Inflammation Is Linked to Psychiatric Disorders

If inflammation remains chronic, it can cause health problems.

Key points

  • Inflammation is the body's defense mechanism against phenomena it recognizes as foreign.
  • If a person's immune system remains chronically activated, it can cause damage to healthy tissue.
  • There are ways to decrease inflammation in one's body through behavioral changes.

When you cut yourself, do you wonder how the wound heals? Perhaps you needed surgery, and during your recovery, you noticed the changing color and texture of your incision. When you develop an infection and raise a fever, do you wonder why? Each of these scenarios describes your body’s response to an assault—it could be infectious, intentional trauma such as an operation, or an accidental injury. The phenomenon that explains how our bodies react when it believes it is under attack is called inflammation.

Inflammation is our body’s defense mechanism against phenomena it recognizes as foreign. However, as with any complicated defense system, an error in the process may occur. Inflammation helps our body fight off bacteria, viruses, and other toxins. But if our immune response continues after the threat has passed, it can cause damage to our healthy tissue.

Inflammation Contributes to Many Health Issues

  • Heart Disease: Heart disease and stroke are linked to the formation of plaques in the walls of our arteries. Our immune system views these plaques as foreign and attempts to protect the body by walling them off. Unfortunately, sometimes these plaques can rupture, and when their contents spill into our bloodstream, they can result in clots, which are implicated in both heart attacks and strokes.
  • Gastrointestinal Disorders: Inflammatory bowel disease (IBD) refers to disorders that involve inflammation of your digestive tract. The most common of these are ulcerative colitis and Crohn’s disease. The precise cause of these disorders remains unclear, but one possibility is a dysfunction of your immune system. When your immune system is fighting off a virus or bacteria, sometimes it goes into “overdrive” and inappropriately attacks the cells in your digestive tract as well as the invading organism.
  • Neurological Disorders: Neuroinflammatory disorders occur when your immune system inappropriately attacks cells in your brain and spinal cord. Perhaps the best known of these disorders is multiple sclerosis, characterized by an immune-mediated response against myelin proteins (i.e., the protective sheath that encases nerve cells). In addition, recent evidence implicates inflammation in some neurodegenerative disorders, such as Alzheimer’s and Parkinson’s disease.
  • Psychiatric Disorders: Recent evidence indicates that chronic inflammation is linked to the development of psychiatric disorders. For example, increased levels of inflammatory proteins have been found in patients with disorders such as schizophrenia and depression.

In animal models, stress was linked to an increase in an inflammatory protein believed to contribute to the development of depression. Inhibition of this protein prevented the development of depression in these animals.

In human studies, blood levels of an inflammatory protein were found in depressed patients compared to healthy volunteers. In one Japanese study, researchers found elevated levels of inflammatory markers in the spinal fluid of depressed patients compared to controls.

How Does Inflammation Lead to Depression?

Cytokine-induced sickness behavior is a syndrome characterized by decreased activity, depression, and loss of energy due to increased circulating levels of proinflammatory proteins called cytokines. These proteins are released during the process of inflammation. In research studies, this syndrome has been proposed as a model for the role the immune system plays in depression.

Interferon-based therapies work by activating an antiviral immune response and are used to treat hepatitis C. In one study, almost 20 percent of the patients receiving this therapy developed psychiatric side effects, mostly depression. However, the symptoms resolved upon discontinuation of treatment. Similar results have been found in patients receiving antiviral treatments for melanoma, a serious skin cancer. Interestingly, these symptoms responded well to antidepressant medication.

The role of inflammation in depression and fatigue led researchers to examine the effects that inflammation in our peripheral nervous system has on our central nervous system. They found that during inflammation, changes occur in the blood-brain barrier, the protective barrier that separates the brain from the peripheral circulation. This barrier becomes more porous during inflammation, allowing the entry of proinflammatory proteins. This has been proposed as a theory for the development of Long COVID, which is associated with psychiatric symptoms, including depression. In animal models, this process was reversed with the use of anti-inflammatory drugs.

What Are Some Ways to Decrease Inflammation?

  • Diet: The adage, “You are what you eat,” is very true. The typical Western diet is full of processed foods, fat, and sugar. Each of these elements can lead to inflammation. A report published in Nature Medicine stated that sugars, grains, and extra salt in ultra-processed foods can change the bacteria in your gut, damage the gut’s lining, and switch on inflammatory genes in cells. Other studies have linked ultra-processed foods to chronic illness and shorter life spans. There is no specific diet to reduce inflammation. However, certain food groups are known to decrease inflammation. They include fruits, vegetables, beans, and whole grains. Omega-3 fatty acids are excellent anti-inflammatory elements. They are found in fatty fish, vegetable oils, walnuts, flaxseeds, and leafy green vegetables.
  • Exercise: Stress can cause your brain to release chemicals that lead to depression or anxiety. In a 12-week study of depressed elderly patients, aquatic exercise decreased depression and anxiety as well as inflammation. After exercise, contracting muscles can release substances that are believed to act as protection against inflammatory proteins. In addition, exercise decreases the amount of fat contained in your major organs. Excess body fat is linked to the activation of inflammatory pathways.
  • Quality Sleep: How well you sleep is more important than how long you sleep. Sleep deprivation is associated with markers of inflammation. The link between sleep deprivation and inflammation is believed to involve your blood vessels. While you sleep, your blood pressure drops as your blood vessels relax. When you are sleep restricted, your blood pressure does not decline as it should, which may lead to inflammation in the walls of your blood vessels. This is possibly one mechanism that explains the link between sleep deprivation and heart disease. The CDC recommends consistency in sleep habits—go to bed and wake up at the same time each day... even on weekends. Make sure your bedroom is quiet, dark, and at a cool temperature. Avoid large meals, caffeine, and alcohol before bedtime. Turn off the screen. Remove all electrical devices from your sleeping area 60 minutes before you want to go to sleep. Screen time activates the part of your brain you want to shut down.
  • Meditate: An article published in The Annals of the New York Academy of Science summarized research findings that involved the effect of mindful meditation on the immune systems of volunteers. The results indicated that mindful meditation helped to modulate proinflammatory effects in their subjects. As a side benefit, it was associated with increased cell-mediated defense mechanisms and increased an enzyme that guards against aging.

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Black, David S., and George M. Slavich. “Mindfulness Meditation and the Immune System: A Systematic Review of Randomized Controlled Trials.” Annals of the New York Academy of Sciences, vol. 1373, no. 1, 2016, pp. 13–24.

Feng, Tami, et al. “Inflammatory Pathways in Psychiatric Disorders: The Case of Schizophrenia and Depression.” Current Behavioral Neuroscience Reports, vol. 7, no. 3, 2020, pp. 128–138.

Lee, Chieh-Hsin, and Fabrizio Giuliani. “The Role of Inflammation in Depression and Fatigue.” Frontiers in Immunology, vol. 10, 2019.

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Zhao, Ruiping. “Inflammatory Biomarkers of Coronary Heart Disease.” Frontiers in Bioscience, vol. 10, no. 1, 2018, pp. 185–196.

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