Could Bacteria Lessen Depression?

Good bacteria and bad bacteria in An unexpected explanation for the rise of 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.

And it all began with a chance observation an oncologist had while using an experimental treatment for lung cancer.

To find out what was going on, Dr Lowry turned to mice. His hypothesis was that the immune response to M. vaccae induces the brain to produce serotonin. This molecule is a neurotransmitter (a chemical messenger between nerve cells) and one symptom of depression is low levels of it.

So we have a study "intriguing for two reasons."
1. the possibility of a vaccination against depression.
2.  a new line of inquiry as to why depression is becoming more common.

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.

I wrote last year in  Can We Be Too Clean?  Apparently so.  Clean living may make us sick and depressed.