A new study on rodents suggests that stomach problems in infancy and early childhood may lead to anxiety and depression later in life.

While digestive problems have been recognized as linked to emotions, the study attempted to address which came first: the stomachache or the stress. Published in PLoS One, the physicians hypothesized that psychological distress resulted from chronic stomach pain rather than as a cause of it.

To test the theory, Pankaj Pasricha, chief of gastroenterology and hepatology at Stanford University School of Medicine, in conjunction with scientists at UC San Francisco and the University of Kansas, injected a mild digestive irritant to 10-day-old lab rats for six days to mimic functional dyspepsia (FD).

Effects Functional Dyspepsia on Lab Rats

FD refers to persistent pain in the upper abdomen, near the ribs. People with FD also experience a sense of fullness, indigestion, bloating, nausea, and heartburn. Many suffer from mood disorders such as anxiety and depression. FD is a common ailment, affecting approximately 20% of the general population.

At 8-10 weeks old, the rats were than subjected to psychological tests to determine if they demonstrated higher anxiety and depression-like behaviors compared to rats in a control group. The results confirmed the theory: the treated rats drank less sugar water, showed significant immobility during swimming tests, and stayed in darker areas longer, avoiding light. They also secreted far greater amounts of various stress hormones after the behavior tests.

The researchers wrote, “In conclusion, our results demonstrate, for the first time, that transient gastric irritation in the neonatal period can induce long-lasting, depression-like, and anxiety-like behaviors…"

Bowel Irritations Leaves Lasting Effects

The study indicates a possible predisposition to developing anxiety or depression in adult life from early abdominal problems, such as infant colic. Anxiety illnesses include Obsessive-Compulsive Disorder, Post-Traumatic Stress Disorder (PTSD), panic disorder, agoraphobia, Generalized Anxiety Disorder and Social Anxiety Disorder. They are characterized by feelings of excessive fear or worry that interfere with daily life. Depressed patients experience a loss of interest in daily activities, intense sadness, and a loss of hope. Depression is considered the leading cause of disability in the US among 15-44 year-olds, and is often linked with anxiety.

In a press release explaining the association, Dr. Pasricha added, "It seems that when the rats are exposed to gastric irritation at the appropriate time there is signaling across the gut to the brain that permanently alters its function."

The study has implications for the treatment of anxiety, depression, and FD with further research underway to understand the biological connection between these disorders.

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