Happiness & Public Policy

From The Economist [thanks FK!]:

Cytokines actually act on sensory nerves that run to the brain from organs such as the heart and the lungs. That action stimulates a brain structure called the dorsal raphe nucleus. It was this nucleus that Dr Lowry focused on. He found a group of cells within it that connect directly to the limbic system, the brain’s emotion-generating area. These cells release serotonin into the limbic system in response to sensory-nerve stimulation.

[…]

This result is intriguing for two reasons. First, it offers the possibility of treating clinical depression with what is, in effect, a vaccination. Indeed, M. vaccae is considered a bit of a wonder-bug in this context. Besides cancer, and now depression, it is being looked at as a way of treating Crohn’s disease (an inflammation of the gut) and rheumatoid arthritis.

Second, it opens a new line of inquiry into why depression is becoming more common. Two other conditions that have increased in frequency recently are asthma and allergies, both of which are caused by the immune system attacking cells of the body it is supposed to protect. One explanation for the rise of these two conditions is the hygiene hypothesis. This suggests a lack of childhood exposure to harmless bugs is leading to improperly primed immune systems, which then go on to look for trouble where none exists.

In the case of depression, a similar explanation may pertain. If an ultra-hygienic environment is not stimulating the interaction between immune system and brain, some people may react badly to the consequent lack of serotonin. No one suggests this is the whole explanation for depression, but it may turn out to be part of it.

I’m skeptical of numbers that show massively increasing depression, but it would be amazing if a good part of what increase there has been is due to our being unnaturally clean, rather than, say, the breakdown of social cohesion in commercial society.