The Link between Inflammation and Depression

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The Link between Inflammation and Depression

Levels of inflammation in the body are known to cause numerous health problems and physical illnesses, but recent research indicates that depression can be strongly linked to inflammation as well. According to a study by researchers from Emory University, high inflammation levels are associated with communication problems between two parts of the brain and a weakening of the reward circuit. People suffering from depression tend to have elevated inflammation levels in their blood and this research strengthens the case proving that the two problems affect one another. Inflammation can contribute to symptoms of depression because of the way that it affects the brain when levels are particularly high.

Inflammation and Its Effect on the Brain
The results of the study were published in Molecular Psychiatry and used 48 participants who were all patients with depression. The findings showed that inflammation is connected with more serious symptoms of depression such as anhedonia which is defined as the inability to experience pleasure. Anhedonia is a symptom that is particularly difficult to treat even among patients that are taking antidepressants.

The results of the study point to possibilities for treatment by blocking inflammation and its effects on the brain. Lowering levels of inflammation in the body could potentially reverse the effects of anhedonia and improve patients’ symptoms. Many of the participants who had high inflammation exhibited a lack of communication in their brain between the ventral striatum and the ventromedial prefrontal cortex. These two regions of the brain normally communicate through functional connectivity which neuroscientists can identify through magnetic resonance imaging.

Patients with high inflammation showed a lack of connectivity in these images while patients with low levels of inflammation showed robust connectivity in these regions. The authors of the study were concerned with brain connectivity between these two regions of the brain because they are important for response to reward.

Confirming Inflammation Causes
The correlation between inflammation and depression remained strong in patients involved in the study even when other variables were accounted for. The authors of the study said that a laboratory test could determine whether or not someone’s specific case of depression was linked to inflammation. Physicians would look for an inflammatory marker in the blood called C-reactive protein or CRP which is a protein made in the liver in response to inflammation.

This test is used for other types of illnesses to determine if a person’s symptoms are related to inflammation. The researcher team was able to test each of the 48 patients to eliminate any underlying medical issues that could have been causing their inflammation. Their CRP was measured over a period of weeks to rule out any infection being the cause. In the depressed patients it was ultimately determined that their inflammation was due to increased stress and obesity which have been shown in numerous studies to increase inflammation in the brain and body.

A previous study found that patients with forms of depression that are difficult to treat along with high inflammation improved in response to an anti-inflammatory antibody. As the next step, the authors of the study plan to test whether L-DOPA, a medicine that targets the brain chemical dopamine, can increase connectivity in regions of the brain related to reward among patients with both depression and high inflammation. Previous research suggests that inflammation leads to reduced dopamine release which could be a major issue in patients with depression and inflammation. Their new studies will be aimed at developing more effective types of treatment for serious symptoms of depression like anhedonia and medications that can be useful for people with both depression and inflammation which can influence each other and worse their symptoms.