Depression and anxiety may result from short-term digestive irritation early in life, a study of laboratory rats by researchers at the Stanford University School of Medicine has indicated.
The findings suggested that some human psychological conditions might be the result, rather than the cause, of gastrointestinal disorders such as irritable bowel syndrome.
"A lot of research has focused on understanding how the mind can influence the body," said Pankaj Pasricha, professor and chief of gastroenterology and hepatology.
"But this study suggests that it can be the other way around. Gastric irritation during the first few days of life may reset the brain into a permanently depressed state," added Pasricha.
To test their hypothesis, the researchers used a laboratory model of functional dyspepsia they had developed years earlier. They subjected 10-day-old laboratory rats to mild stomach irritation daily for six days.
"We hypothesized that this treatment might also be affecting the development of central nervous system, and driving the animals to anxiety and depression," said Pasricha.
Indeed, as the researchers assessed the behaviour of the treated rats when the animals were 8 to 10 weeks old, they found that those rats with early gastric irritation were significantly more likely than their peers to display depressed and anxious behaviours including a decreased consumption of sugar water, less-active swimming in a pool of warm water and a preference for dark rather than light areas in a maze.
"It seems that when the rats are exposed to gastric irritation at the appropriate point in time," said Pasricha, "there is signaling across the gut to the brain that permanently alters its function."
The study has been published in the PLoS One.