Reconceptualizing major depressive disorder as an infectious disease

In this article, I argue for a reconceptualization of major depressive disorder (major
depression) as an infectious disease. I suggest that major depression may result from
a parasitic, bacterial, or viral infection and present examples that illustrate possible
pathways by which these microorganisms could contribute to the etiology of major depression.
I also argue that the reconceptualization of the human body as an ecosystem for these
microorganisms and the human genome as a host for non-human exogenous sequences may
greatly amplify the opportunity to discover genetic links to the illness. Deliberately
speculative, this article is intended to stimulate novel research approaches and expand
the circle of researchers taking aim at this vexing illne