The immune system is an unbelievably intricate web of interactions. It helps determine what is us or non-threatening from what is dangerous. It helps us fight infections through cascading reactions. It facilitates healing from injuries. It knows if the foreign microbe we are dealing with is a bacteria, virus, parasite, allergen, or food and mounts the appropriate response for each. It is located all over the body, but mostly in the gut.
The immune system communicates via chemical messengers called cytokines. Cytokines help the cells of the immune system communicate with one another to initiate the appropriate immune response. Cytokines can be either pro-inflammatory or anti-inflammatory. There are three main inflammatory cytokines: Interleukin (IL) 1, IL-6, and tumor necrosis factor alpha (TNF-a).
What does this have to do with anxiety and depression? The term “inflammation” basically refers to an elevation of the inflammatory cytokines (IL-1, IL-6, and TNF-a) as instigated by the immune system. These cytokines have been associated with the feelings of malaise/fatigue/depression, anxiety, and hostility/irritability, collectively referred to as sickness behaviors. When you have inflammation in your body, your immune system is pumping out more of these cytokines and increasing your chances of experiencing these symptoms.
Cytokines and sickness behaviors
- IL-1: Associated with malaise, fatigue, and depression (Maes, Song, & Yirmiya, 2012; Berk et al., 2013)
- IL-6: Associated with anxiety (O'Donovan et al., 2010)
- TNF-a: Associated with hostility and irritability (Suarex, Lewis, & Kuhn, 2002)
It is important to note that inflammation is a natural and necessary part of the body's defense and healing responses. We need inflammation to fight infections and heal. But being exposed to inflammation on an ongoing basis is bad news. It is meant to be a short-term process. If it turns chronic, a whole host of symptoms can arise. In fact, most disease processes are associated with inflammation. As Dr. Robert Rountree describes in, The Textbook of Functional Medicine (2010), while acute inflammation can be likened to an obvious roaring inferno, chronic inflammation is like a "slow, smoldering fire with intermittent eruptions." Since chronic inflammation is present in lower levels, it often gets overlooked, but this slow smoldering can have serious consequences. In addition to anxiety and depression, chronic inflammation has been associated with a wide range of conditions including asthma, eczema, osteoarthritis, rheumatoid arthritis, lupus, neurodegenerative disorders, diabetes, and cardiovascular disease (Rountree, 2010).
The digestive tract houses over 70% of the immune system. This makes food a powerful tool for turning inflammation on or off. A diet high in sugar, refined grains, flours, trans fat, processed vegetable oils, processed foods, soda, and sweets is a recipe for chronic inflammation. On the other hand, you can use food to turn down inflammation by consuming ample amounts of fresh fruits and vegetables, omega-3-rich foods, herbs, and spices, and by sourcing meats and seafood that have been pastured or wild caught.
Poor food choice isn’t the only instigator of chronic inflammation. Other variables include gut dysbiosis (imbalanced gut bacteria), gut pathogens, high stress, gut hyper-permeability (aka, leaky gut), and toxic exposure from the environment, personal care products, building materials, plastics, or heavy metals. Several inflammatory variables are often present at once.
If you suffer from anxiety or depression, it may be in your interest to look into underlying causes of inflammation that might be exacerbating your symptoms. If you're able to restore balance and create a healthier inner environment, you might be surprised to notice anxiety settle and depression lift.
Berk, M., Williams, L.J., Jacka, F.N., O’Neil, A., Pasco, J.A., Moylan, S., Allen, N.B., Stuart, A.L., Hayley, A.C., Byrne, M.L., & Maes, M. (2013). So depression is an inflammatory disease, but where does the inflammation come from? BMC Medicine, 11(200). Retrieved from https://bmcmedicine.biomedcentral.com/articles/10.1186/1741-7015-11-200
Maes, M., Song, C., & Yirmiya, R. (2012). Targeting IL-1 in depression. Expert Opinion on Therapeutic Targets, 16(11). Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/22925041
O’Donovan, A., Hughes, B.M., Slavich, G.M., Lynch, L., Cronin, M.T., O’Farrelly, C., & Malone, K.M. (2010). Clinical anxiety, cortisol and interleukin-6: evidence for specificity in emotion-biology relationships. Brain, Behavior, and Immunity, 24(7). Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/20227485
Rountree, R. (2010). Immune Imbalances and Inflammation. In D.S. Jones (Ed.), Textbook of Functional Medicine (p. 308). Federal Way, WA: Institute for Functional Medicine.
Suarez, E.C., Lewis, J.G., & Kuhn, C. (2002). The relation of aggression, hostility, and anger to lipopolysaccharide-stimulated tumor necrosis factor (TNF)-alpha by blood monocytes from normal men. Brain, Behavior, and Immunity, 16(6), 675-684. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/12480498