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Chapter 1. Chapter

Article

From the Pages of Scientific American

Inflammation Brings on the Blues

From the pages of Scientific American. Inflammation Brings on the Blues. Our immune system may mean well, but it might also cause depression. As if being stuck sick in bed wasn't bad enough, several studies conducted during the past few years have found that the immune response to illness can cause depression. Recently scientists have pinpointed an enzyme that could be the culprit, as it is linked to both chronic inflammation—such as that found in patients with coronary heart disease, type 2 diabetes and rheumatoid arthritis—and depressive symptoms in mice. In the new study, immunophysiologist Keith Kelley and his colleagues at the University of Illinois exposed mice to a tuberculosis vaccine that produces a low-grade, chronic inflammation. After inoculation, production in the mice brains of an enzyme called IDO, which breaks down tryptophan, spiked. The animals exhibited normal symptoms of illness such as moving around and eating less. Yet even after recovering from the physical illness induced by the vaccine, they showed signs of depression—for example, struggling less than control mice to escape from a bucket of water. Surprisingly, their listlessness was solved relatively simply. “If you block IDO, genetically or pharmaceutically, depression goes away” without interfering with the immune response, Kelley explains. The research makes a solid case that the immune system communicates directly with the nervous system and affects important health-related behaviors such as depression. The findings could bring relief to patients afflicted with obesity, which leads to chronic inflammation, as well as to cancer patients treated with radiation and chemotherapy drugs that produce both inflammation and depression. “IDO is a new target for drug companies to aim for, to treat patients with both clinical depression and systemic inflammation,” Kelley says. The author is Corey Binns. Reproduced with permission. Copyright 2009 Scientific American, a division of Nature America, Inc. All rights reserved.

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1.1 Quiz

1. Kelley and colleagues’ work on inflammation and its relationship to depression find that the link between the two comes in the form of:

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2. How did the study discussed in the excerpt create inflammation in its experimental animals?

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3. Which statement accurately describes the experimenters’ evidence that inflammation led to the production of a substance that in turn led to depression?

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4. Kelley and his colleagues believe that the discovery of this inflammation-related substance’s effect on depression is important because:

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5. One of the theories of depression that might be impacted by Kelley and colleagues’ work is _____, which suggests that depression arises from a feeling that people can’t control negative outcomes.

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