Depressed? Could be the flu.

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A new report by Vanderbilt University reveals a link between depression and inflammatory infection in the brain. Published in the December 2010 issue of Neuropsychopharmacology,  these new findings, scientists hope, will bring us closer to understanding the correlation between mental illness and influenza.

Says Dr. Randy Blakely, PhD, director of the Vanderbilt Center for Molecular Neuroscience, “Many people exhibit signs of lethargy and depressed mood during flu-like illnesses.  Generally these have been treated as just a consequence of being physically ill, but we think there is likely to be something more brain-centric at work here.”

As part of the Vanderbilt University experiment, rats were injected with inflammatory “flu” cytokines, a chemical which is produced when the body is under attack by influenza. Inflammatory cytokines trigger serotonin transporters (SERT), which inhibit the production of serotonin.

As a result of the diminished level of serotonin affected by increased SERT levels, test rats exhibited behaviors suggesting extreme anxiety and despair. Conversely, rats who were given the cytokines who did not carry the SERT gene showed no change in behavior at all.

SSRIs (selective serotonin reuptake inhibitors) such as Prozac and Zoloft are prescribed to patients who suffer from severe depression, anxiety and obsessive compulsive disorders.  These findings suggest that flu viruses might counter SSRI’s ability to regulate serotonin levels in treating depression.

Scientists hope to use this information to reverse cytokine production during the flu season.