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Our immune system’s reaction to serious infection, injury and stress may actually cause or worsen some types of depression, according to a Science Newsarticle published July 4. Though the new report doesn’t apply specifically to HIV, it is possible that chronic over-stimulation of the immune system in response to the virus may increase the risk of depression and fatigue.
When the body is stressed because of an infection or trauma, it produces dozens of chemical messengers called cytokines. Some cytokines signal the brain and endocrine system to slow us down, prompting us to feel tired and want to rest. While this forces the body to focus its energy on the healing process, it can also cause or worsen symptoms of depression. This has been documented in people being treated for hepatitis C virus (HCV) and certain cancers, half of whom experience depression as a side effect of the immune-stimulating treatment interferon-alpha. In a related finding, scientists have discovered that people who are depressed, but otherwise healthy, have elevated levels of many immune cytokines.
Scientists have begun studying how chronic stimulation and inflammation of the immune system by diseases such as hepatitis, arthritis and HIV may actually cause or worsen a depressed mood. A 2006 study by the pharmaceutical company Amgen found that people who had hyperactive immune systems from the skin condition psoriasis had improvements in mood when they took the company’s cytokine blocker Enbrel (etanercept).
While researchers are increasingly interested in the potential to treat depression by manipulating the immune system, they are proceeding with caution, the Science News article reports. Many of the cytokines associated with depression, such as tumor necrosis factor, interferon-alpha and interferon-beta, are vital to mounting effective immune responses to infections and cancers. Thus, simply blocking or lowering their numbers could have dangerous repercussions. Scientists are actively investigating the ways that cytokines interact with brain chemicals and hormones, however, in hopes of finding safer ways to blunt the mood effects of immune inflammation.
