Bacteria and Depression

Bacteria cause disease. The idea that they might also prevent disease is counterintuitive. Yet that is the hypothesis Chris Lowry, of Bristol University, and his colleagues are putting forward in Neuroscience. They think a particular sort of bacterium might alleviate clinical depression.

The chance observation that Dr Lowry followed up to arrive at this conclusion was made by Mary O'Brien, an oncologist at the Royal Marsden Hospital in London. Dr O'Brien was trying out an experimental treatment for lung cancer that involved inoculating patients with Mycobacterium vaccae. This is a harmless relative of the bugs that cause tuberculosis and leprosy that had, in this case, been rendered even more harmless by killing it. When Dr O'Brien gave the inoculation, she observed not only fewer symptoms of the cancer, but also an improvement in her patients' emotional health, vitality and general cognitive function.

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.

Interesting. In the future there might be a vaccine against depression.

via The Economist