Scientists at University College Cork (UCC) have found that mice who were raised without bacteria in their gut showed autistic patterns of behavior. Scientists argue that their findings demonstrate the crucial role stomach bacteria plays in the development of normal social behavior.



Professor Ted Dinan, psychiatry professor and a principal investigator in the Alimentary Pharmabiotic Centre (APC), said the core of their paper argued that animals need a normal range of bacteria in their gut in order for normal social development. The APC has been studying the impact of gut bacteria on the brain for years. Their findings were published on May 21, 2013 in Molecular Psychiatry, the leading international psychiatry journal.



Dinan said, “In our studies involving mice, we found animals raised in a germ-free environment (without microbiota in their gut) spent more time interacting with objects than other animals and so have distinctively autistic patterns of behavior.”



He said that the serotonin system, which helps regulate mood, does not develop properly if there is not enough bacteria in the gut. Mice in the study who did not have enough bacteria were less interested in new social situations than mice with a normal level of bacteria. Bacteria deficient mice also exhibited repetitive behaviors and displayed repetitive grooming when placed in a new situation.



The scientists said that the bacteria deficient mice behavior resembles social cognition deficits of patients. Children with autism also show repetitive behaviors and scientists pointed out that gut problems are common among those with autism.



Scientists weaned bacteria and then added it and this reversed the mice’s social avoidance and repetitive behaviors, but had no impact on social cognition impairments.



The new findings have shown what scientists need to study further. Professor John F. Cyran, senior author of the publication and head of the Department of Anatomy and Neuroscience at UCC said about the experimental models, “they clearly highlight that the absence of critical bacteria during early life affects behaviors relevant to autism and thus further investigations into how the microbiota affects the wiring of the brain are required.”