Could Cleanliness Be Causing Depression?

New research hints that a too-clean environment may contribute to depression.

The Economist reports that London oncologist Mary O'Brien made the serendipitious discovery that cancer patients who received an experimental innoculation of dead M. vaccae bacteria as part of a cancer drug test also improved their mental states.

Dr. Chris Lowry of Bristol University (UK) looked into the mystery and concluded that the body's immune response to the invading bacteria includes production of more serotonin. Serotonin aids in the transmission of messages in the brain, and low levels are linked to depression.

His research team was able to track the immune response in mice and the subsequent activation of the portion of the brain that produces serotonin.

And the final step -- showing that they were happier mice? The Economist tells us "Previous research has shown that unstressed mice enjoy swimming, while stressed ones do not. (Lowry's) mice swam around enthusiastically."

A normal level of exposure to the bacteria (mycobacterium vaccae is normally found in dirt) could spark the production of serotonin in some people; without the exposure, they could feel depressed.

Depression is frequently and incorrectly lumped together with other midlife problems as "midlife crisis."

The new research adds to the evidence supporting the notion that too hygienic an environment, especially when young, can actually degrade long term health. The increased incidence of asthma and allergies could be one manifestation of this problem; higher levels of depression could be another.

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Press release here; Times of London report here.