Inflammation May Be Causing Depression in About One-Third of Patients

(Corbis)

While it’s understood that inflammation can cause aches and pain throughout the body, researchers from Emory University have discovered that inflammation can also affect those suffering from depression.

According to the study authors, high levels of inflammation is associated with a “failure to communicate” between two parts of the brain—the ventral striatum and the ventromedial prefrontal cortex. And approximately one-third of people diagnosed with depression have markers of elevated inflammation levels in their blood.

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These results, which were published in the journal Molecular Psychiatry, also indicate that chronic inflammation can affect the brain in ways that are connected with stubborn symptoms of depression, such as anhedonia (defined as the inability to experience pleasure), which can be difficult to treat.

So how exactly does anhedonia differ from other types of depression?

“The diagnosis of major depressive disorder (MDD) is made up of a number of symptoms,” lead researcher Jennifer C. Felger, PhD, MS, assistant professor of psychiatry and behavioral sciences at Emory University School of Medicine and Winship Cancer Institute, tells Yahoo Health. “The two core symptoms of depression are depressed mood and anhedonia, one of which must be present to make a diagnosis of MDD. Thus, most depressed exhibit some level of anhedonia as part of their illness.”

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Felger adds that a simple laboratory test can determine whether or not someone’s specific case of depression is linked to inflammation. Physicians would be looking for “an inflammatory marker in the blood called C-reactive protein (CRP), which is a protein made in the liver in response to inflammation,” she explains. “It has been used clinically to determine risk for cardiovascular disease, but is also increased in a number of other diseases such as inflammatory and autoimmune diseases, metabolic disorders and cancer.”

In this current study, Felger and researcher team tested the 48 participants in order to eliminate other underlying medical issues that may have been causing their inflammation.

“CRP was also measured over a period of weeks to ensure that inflammation levels were stable and to rule out an acute infection, like a cold or flu,” she states. “In our sample of depressed patients, the high levels of inflammation observed was most likely related to increased stress and obesity, which have been shown in a number of studies in humans and laboratory animals to increased inflammation in the brain and in the body.”

Felger will be conducting further research to find out if L-DOPA, a medicine that targets the brain chemical dopamine, can increase connectivity in reward-related brain regions in patients who are suffering from inflammation-linked depression.

“We hope our investigations may lead to new therapies to treat anhedonia in high-inflammation depression,” she concludes.

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