Neural Response to Inflammatory Challenge in Major Depressive Disorder
This is a parallel group, double-blinded, placebo-controlled study. Participants with MDD (n=90) and HC (n=90) will be randomly assigned (2:1) to receive either lipopolysaccharide (LPS) (0.8ng/kg of body weight) or placebo (same volume of 0.9% saline) administered as an intravenous bolus. This will yield the following groups: MDD-LPS (n=60), MDD-Placebo (n=30), HC-LPS (n=60), HC-placebo (n=30). There are three main aims: to identify immune pathways and neural circuits that respond differently to LPS in MDD vs. HC subjects; (2) to test whether the strength of inflammatory changes induced by LPS is associated with degree of change in anhedonic symptoms and neural circuits in the MDD group, and (3) to identify a biotype of MDD that shows a differential immunological and neurophysiological response to LPS. The main outcome variables are symptoms of anhedonia measured with the Snaith-Hamilton Pleasure Scale (SHAPS), cytokines (Il-6, IL-8, IL-10, and TNF), and BOLD signal change in the neural circuitry mediating interoceptive processing, i.e. the insula and cingulate cortex. The exploratory aim is to determine whether the acute inflammatory response to LPS can predict the clinical course of depression over a period of six months. The main outcome of this component of the study is self-reported depressive symptoms assessed with the QIDS-SR.
• Both healthy controls and depressed participants will be required to be in good general health (as evaluated during Visit 1, including EKG) and to be 18-65 years of age. A DSM-V diagnosis of MDD will be made with the MINI International Neuropsychiatric Interview and current symptoms of depression will be measured with the clinician-administered MADRS and the self-report PHQ-9. Depressed participants will be required to have symptoms of depression (i.e. a PHQ-9 score ≥10) and/or a MADRS score of ≥7.