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Inflammation and Depression: Complicated Connections

     

Growing evidence shows an association between depression and inflammation. But the connections are complex and not well understood. Understanding these links is important because it could lead to better depression treatment, especially for the many people who don’t respond to traditional treatments.

Inflammation is the body’s response to protect itself and it can be acute or chronic. Redness and swelling around a cut or other injury or the response to an infection like the flu are examples of acute inflammation. Chronic inflammation can occur in response to substances in the body, such as toxins from cigarette smoke or an excess of fat cells. (1)

Inflammation can affect the brain and behavior and can affect the way a person responds to treatment. Inflammation plays a key role in the development of depression for some people, but not for all. That difference may help explain why some people don’t respond to traditional depression treatment. The most common type of anti-depressant medication, SSRIs, work on the brain’s neurotransmitters such as serotonin and dopamine. While they provide significant benefit for many people who live with depression, they don’t work for everyone. Approximately one third of all patients with depression fail to respond to conventional antidepressant therapies.(2)

The connections between depression and inflammation likely work in both directions.(2) Increased inflammation is a risk factor for depression and depression has been found to contribute to increased inflammation. And the direction of effects may differ for men and women. A 2018 study found that “symptoms of depression predicted increasing inflammation for men, but not for women, and inflammation predicted worsening depression for women, but not for men.” (3) One large study, reported in the American Journal of Psychiatry, looking at the linkages between depression and inflammation concludes that “the bidirectional links between depression, inflammation, and disease suggest that effective depression treatments could have a far-reaching impact on mood, inflammation, and health.” (4)

Although more research is needed on types of treatment and who might potentially benefit, anti-inflammatory treatments may offer a new option for some people with depression.

Reducing inflammation

In addition to anti-inflammatory medications, there are a number of lifestyle changes that can help reduce inflammation and improve overall health. For example, weight loss, exercise, sufficient sleep, meditation and yoga can all lower inflammation. Certain foods can also reduce inflammation while other foods can increase it. Foods that can contribute to inflammation are many of the foods generally considered bad for your health (5), such as

  • refined carbohydrates, such as white bread and pastries
  • fried foods
  • soda and other sugar-sweetened beverages
  • red meat (burgers, steaks) and processed meat (hot dogs, sausage)
  • margarine and shortening

Foods that can help combat inflammation, and provide other health benefits, include:

  • green leafy vegetables, such as spinach, kale and collards
  • nuts like almonds and walnuts
  • fatty fish like salmon, mackerel, tuna and sardines
  • fruits such as strawberries, blueberries, cherries and oranges
  • tomatoes
  • olive oil

While there are still many questions about the how these processes work, new research on inflammation holds the potential for better treatments for depression, especially for those with treatment resistant depression.

References/Resources

  • (1) Harvard Heart Letter. 2017. What is Inflammation?
  • (2) Kohler, O, et al. Inflammation in Depression and the Potential for Anti-inflammatory Treatment. Current Neuropharmacology. 2016, Vol. 14, No. 0.
  • (3) Niles AN, et al. Gender differences in longitudinal relationships between depression and anxiety symptoms and inflammation in the health and retirement study. Psychoneuroendocrinology. 2018, 28(95):149-157.
  • (4) Kiecolt-Glaser Jk, Derry HM, Fagundes CP. Inflammation: depression fans the flames and feasts on the heat. Am J Psychiatry. 2015, 172(11):1075-91.
  • (5 )Harvard Women's Health Watch. Foods that fight inflammation. Updated: August 13, 2017
  • Mcintyre RS, Rong C. Where There’s Smoke, There’s Fire. Psychiatric Times. May 31, 2018. Vol 35 issue 5.
  • Soledad Cepeda, M., Stang, P., & Makadia R. (2016) Depression Is Associated With High Levels of C-Reactive Protein and Low Levels of Fractional Exhaled Nitric Oxide: Results From the 2007-2012 National Health and Nutrition Examination Surveys. J Clin Psychiatry. 1666-71.
  • Kiecolt-Glaser JK, Derry HM, Fagundes CP. Inflammation: depression fans the flames and feasts on the heat. Am J Psychiatry. 2015 Nov 1;172(11):1075-91.
  • DiSalvo, D. Could Depression Be An Immune Response To Stress? A New Study Suggests An Answer. Forbes. July 23, 2018.

     

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