A study conducted by a team of researchers at the McMaster University in Hamilton, Canada, states that depression and anxiety may have a connection with the microbes present in the intestines. The researchers believe that gut bacteria trigger the behavioral signs associated with stress.

The researchers conducted their study on a group of mice. The study, which has been published in the journal Nature Communications, showed that the laboratory mice exhibited signs of anxiety and depression-like behavior when exposed to stress, but only when gut bacteria were present in them. The researchers thus concluded that gut microbiota trigger the behavioral signs of stress.

“We have shown for the first time in an established mouse model of anxiety and depression that bacteria play a crucial role in inducing this abnormal behavior,” Premysl Bercik, the lead author of the study, said.

During the experiment, the researchers observed that mice that have had the stressful experience early in life, such as separation from the mother, showed greater signs of depression and anxiety, including isolated behavior. In addition, such mice have higher levels of stress hormone corticosterone in their blood.

However, the researchers discovered that when germ-free mice with no intestinal bacteria were exposed to similar stress, they showed no signs of depression or anxiety later in life. The team noted that they have similar levels of corticosterone in their blood, too, as that of the group of mice with gut bacteria.

The research team is now planning to conduct further research to see if the study results are applicable to humans as well. The researchers want to see further if the medications that target intestinal bacteria can help treat patients with psychiatric disorders.