Researchers demonstrate that high levels of interferon-alpha in cerebrospinal fluid are associated with low serotonin concentrations and symptoms of depression.
Interferon is a mixture of proteins that the body makes in the even of viral infection. It has direct antiviral activity and also activates the portion of the immune system which is designed to deal with viruses. In this way specific immune chemicals are produced which aid in fighting off the virus. Interferon is divided into different types labelled alfa, beta, and gamma.
Interferon-alpha (IFN-alpha) is produced as a medicine through genetic engineering processes and used as a treatment in viral diseases, particularly viral hepatitis.
It is well known that side-effects of IFN-aplha therapy include mood disturbances including depression, anxiety, irritablility and insomnia but the exact reasons for this are still being determined. Now researchers from the Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia (USA) have pinpointed an association between higher levels of IFN-alpha and lower serotonin concentrations.
The scientists studied twenty-four patients with hepatitis C, half of whom were given IFN-alpha therapy and half were not. They detected IFN-alpha in the cerobrospinal fluid (CSF) of all treated patients and only one control. Results showed that IFN-alpha concentrations in CSF were inversely related to the concentration of serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in CSF. Low levels of 5-HIAA were associated with depressive symptoms.
This research illustrates another example of how the immune system interacts with the nervous system and affects its function. The researchers conclude that IFN-alpha therapy is able to activate an inflammatory response in the central nervous system of humans that interacts with serotonin metabolism and that this is associated with depression.
This two-way interaction between the immune system and nervous system (and hormonal system) is now recognised and studied under the name neuroendocrinimmunology.
This research is also important for understanding illnesses such as chronic fatigue syndrome (ME/CFS) and fibromyalgia and why depression is more common in people suffering from them.
These illnesses have been strongly associated with viral infections and chronic activation of the part of the immune system that deals with them. This of course means production of IFN-alpha and associated chemicals. Given this latest research on IFN-alpha and its interaction with serotonin metabolism it is no wonder depression is common amongst ME/CFS and fibromyalgia patients.