Major depressive disorder is the most common type of depression and involves severe symptoms that interfere with an individual’s ability to work, sleep, study, eat, and enjoy life. Each year, about 6.7 percent of U.S. adults are affected by the condition, with women 70 percent more likely to be affected than men.

Scientists do not have a good handle on what actually causes depression. In some cases, a traumatic event can trigger its onset, but in other cases, no obvious trigger is evident. In a recent study published in the journal Biology of Mood & Anxiety Disorders, Turhan Canli, PhD, suggests that major depression be reconceptualized as an infectious disease.

Camli presents three arguments for why major depressive disorder should be considered an infectious disease:

  • Patients with major depressive disorder exhibit sickness behaviors such as loss of energy and feelings of illness. He sites inflammatory biomarkers as indicators of an illness-related origin.
  • Parasites, bacteria, and viruses are known to alter emotional behavior in infected individuals.
  • The human body is an ecosystem for microorganisms that are intricately related to the role of genetics.

“Deliberately speculative, this article is intended to stimulate novel research approaches and expand the circle of researchers taking aim at this vexing illness,” noted Canli.

Dr. Smith and I have blogged on this topic before. A number of studies point to alterations of mental status being linked to inflammation that originates from an infectious process somewhere in the body (often, the gut). This finding has the potential to greatly change how depression is researched and treated. I hope that others listen to Dr. Canli’s recommendations, which are currently way ahead of most others in his field.