These little guys may be doing the thinking for you. Science Daily reports:
For the first time, researchers have conclusive evidence that bacteria residing in the gut influence brain chemistry and behavior.
The findings are important because several common types of gastrointestinal disease, including irritable bowel syndrome, are frequently associated with anxiety or depression. In addition there has been speculation that some psychiatric disorders, such as late onset autism, may be associated with an abnormal bacterial content in the gut.
For each person, the gut is home to about 1,000 trillion vital bacteria with which we live in harmony. Any disruption can result in life-threatening conditions, such as antibiotic-induced colitis.
Working with healthy adult mice, the researchers showed that disrupting the normal bacterial content of the gut with antibiotics produced changes in behavior; the mice became less cautious or anxious. This change was accompanied by an increase in brain-derived neurotrophic factor (BDNF), which has been linked to depression and anxiety.