Since ancient times, mind control has been one of the holy grails of human manipulation. Militaries in particular have been looking for ways to create the "Manchurian Candidate" through a variety of means including hypnosis, electric shock, drugs and "neurosurgical techniques," which include lobotomies. On the flip side, advertising agencies and social marketers have worked on developing thought influencing strategies, such as the subtle science of "suggestology" to keep people loyal to a brand or particular conduct. Yet whether the intent is to develop the perfect soldier, open the wallets of consumers, or use "The Force", the means to influence the mind has been hard to resolve.
For germs, however, mind control is business as usual.
The impact of microbes on mental function has been known for centuries, thanks in part to the neuropsychiatric effects of syphilis and rabies. The focus on the mental effects of germs didn't really take hold until the 1980s when HIV patients were beginning to exhibit signs of dementia. This opened up a widespread hunt for other germs that might have deleterious effects on our brain function.
What has been found is quite honestly amazing.
There are now close to a dozen pathogens that are known to cause psychological dysfunction from mania to schizophrenia to depression. This cast of mind-altering pathogens can come from almost anywhere. Some, like syphilis, are sexually transmitted including chlamydia and herpes. Others, such as the cat parasite, Toxoplasma gondii, the bacteria that cause lyme disease, Borrelia burgodoferi, and Brucella suis, which causes brucellosis are all zoonotic in that they come from animals, just like rabies. Even the cause of strep throat, streptococcal bacteria, has been related to the development of obsessive-compulsive disorder and anorexia nervosa.
As the list of negative psychological effects of microbes increases, some researchers have started to investigate whether microbes could have an alternate effect on the brain by making life better. Much like their advertising counterparts, these researchers believe that there exists a more subtle, lighter side to microbial mind control.
Borrowing from an old adage, these researchers have found that the key to a happier life is found in a happy gut.
The initial intent of research into beneficial bacteria was not about trying to please the mind but actually to stop the pain associated with irritable bowel syndrome (IBS) and colitis. The use of gut-friendly bacteria, known as probiotics, appeared to help patients with the symptoms associated with IBS and also appeared to help improve their overall quality of life.
There was little investigation on the psychological benefit but as time wore on, more people started to investigate whether there was any link between good bacteria and a more pleasant life. A few years later, in 2007, that all changed when a group out of the Institut National de la Santé et de la Recherche Médicale (INSERM) in France found that certain probiotics happened to trigger opioid and cannabinoid receptors in the gut, producing an effect similar to morphine.
As soon as that publication came out, the race was on to find the ultimate mood enhancing bacteria.
Microbiome studies have now become popular as has research into various kinds of probiotics and their beneficial helpers, prebiotics. The results have shown that gut bacteria can have psychotropic actions that can ultimately calm a person down and even control anxiety. Moreover, these happy harbingers could potentially reverse other problems caused by infections including cognitive dysfunction and depression. Probiotics might even be sold as mood enhancers and mimics of other more addictive -- and less legal -- substances.
The future of research into microbial mind control is without a doubt bright although it will inevitably separate into two paths. One will focus on the deleterious effects of infection on the brain while the other will focus on the use of microbes in the "second brain" to improve one's quality of life. The science is still in its infancy and many more revelations are certain to come. But as our understanding grows, so will our realization that despite all the efforts taken over the millennia to force a person's behaviour, the answer has been right in front of us all along in the day to day activities of germs.