There’s long been speculation that gut disorders like irritable bowel syndrome are linked to mood disorders like anxiety and depression. Now, there’s much better proof of a connection. The elimination of bacteria in the bowels causes changes to the brain, according to new research by McMaster University scientists published in the journal Gastroenterology. The researchers showed that disrupting normal bacterial content in the gut of mice with antibiotics made the mice less cautious or anxious, while simultaneously increasing brain derived neurotrophic factor (BDNF), a substance that has been linked to depression and anxiety. The researchers told the McMaster Daily News that the next step is exploring whether probiotic bacteria can be used to treat mood disorders, particularly those associated with gastrointestinal problems.