Depression A Non-contagious, Infectious Disease?


Some scientists are trying to solve the puzzle of depression by thinking outside the box. Turhan Canli, for instance, suggests that depression may be a non-contagious, infectious disease.

Canli, of Stony Brook University in New York, wonders whether an unknown pathogen(s) is the primary cause of depression. As pathogens do, it would trigger an inflammatory response by the immune system to ward off the infection. So treating the inflammatory response will bring symptom relief but not eliminate depression’s cause.

A pathogen causing MDD, or major depressive disorder, would specifically target the nervous system. An individual carrying the pathogen may have no symptoms until the pathogen is activated by another factor, such as a stressful life circumstance. This same mechanism could also be responsible for other mental health disorders such a bipolar disorder or PTSD.

Why Infection Makes Sense

Making a case for depression being an infectious disease rests on several biology-based arguments.

  1. People who have MDD also act physically ill. They have trouble getting out of bed, have low energy and lose interest in activities. Canli also points out the individuals not steeped in Western medicine traditions report mostly somatic (physical) symptoms when they are depressed, instead of affective (emotion, mood) symptoms.
  2. Research has associated depression with inflammation of the brain tissue. Inflammation is an indicator of an immune response to a pathogen. A pathogen can be a parasite, bacterium or a virus. Nature provides many examples of these pathogens causing changes in the emotional behavior of complex organisms.
  3. Scientists’ search for specific depression causing genes has not been successful. This search has been done on the human genes within our system, but eight percent of our human genome is based on chains of retroviruses. It is possible that depression causing retrovirus sequences could be triggered by stressful events.
  4. The human body is a repository for countless undetected bacteria and viruses that can be passed from parents to their children.

Turhan Canli is not alone in suggesting that depression may be an infectious disease.

Not A Psychiatric Condition

George Slavich, a clinical psychologist at the University of California, has been researching depression for years.

“I don’t even talk about it [depression] as a psychiatric condition any more,” said Slavich. “It does involve psychology, but it also involves equal parts of biology and physical health.”

Like Canli, Slavich points out that people feel miserable when they have an infectious disease. They get bored, fatigued, irritable and just want to lie on the couch. This also describes many people with depression and suggests there may be a common cause. Slavich sees inflammation as a sign that the immune system is fighting an infectious intruder.

Other scientists are skeptical of the pathogen-depression connection since the inflammation associated with depression can also be triggered by a poor diet, obesity and even loneliness. Still, the arguments for depression being an infectious illness are compelling. Scientists such as Canli hope for extensive research into this possibility.

Sources: Biology of Mood and Anxiety Disorders; The Guardian
Photo credit: Spam / flickr creative commons


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