Influenza Challenge in Mood Disorders

The aim of this project is to evaluate the efficacy of the influenza vaccine in individuals with major depressive disorder (MDD) as well as to elucidate the nature of the immunological abnormalities in MDD using a quasi-experimental design. Specifically, the investigators plan to induce transient, mild inflammation in medically-healthy study participants using the influenza vaccine. Initially the investigators will conduct a pilot project with up to 20 individuals in order to evaluate the time-point at which the peak inflammatory response to the vaccine occurs. Subjects will receive the seasonal influenza vaccine and provide blood samples 4 hours, 2 days, and 30 days post vaccination. Subsequent to the pilot study, both depressed and psychiatrically-healthy participants will be randomized in a parallel group, double-blind design so that they receive either influenza vaccine (seasonal vaccine) or saline (i.m). At baseline, subjects will provide a blood sample, complete a number of rating scales to measure mood and fatigue, and may complete approximately one hour of MRI scanning with or without simultaneous EEG recording. Two-days post vaccination, they will provide a second blood sample, complete more clinical ratings and may complete another identical MRI session with or without simultaneous EEG. Four weeks later, participants will be asked to return to provide a third blood sample and complete additional clinical ratings. The blood samples will be used to measure both innate and adaptive immune function and may be used to correlate the vaccine-induced immunological changes to neurophysiological changes in the brain measured by MRI and/or EEG.