Chronic constipation often accompanies depression. Using a mouse model, researchers investigated why this relationship might occur. They have also tested an experimental drug with encouraging results. Share on Pinterest Depression and constipation often go hand in hand. Over the years, scientists have found strong links between psychiatric disorders and an increased risk of constipation, particularly in older adults. Around one-third of people with depression experience constipation and, according to some reports, it plays a significant role in reducing the perceived quality of life of these individuals. Some depression medications are known to reduce gut motility and slow bowel movements, but researchers believe that this fact alone cannot explain all cases of constipation. Recently, a group of researchers from Columbia University Irving Medical Center in New York decided to investigate this question in more detail. Specifically, they were interested in the role of the neurotransmitter serotonin. Study lead Dr. Kara Gross Margolis explains why she and her colleagues were interested in this topic. “Ultimately, many patients with depression are faced with limited treatment options and have to suffer with prominent [gastrointestinal] dysfunction,” she said.

What do we already know? Some scientists refer to the stomach as our “second brain.” Perhaps surprisingly, it has more neurons than the spinal cord, and it operates with a similar suite of neurotransmitters as the brain. The researchers behind the latest study were particularly interested in serotonin because people with depression are thought to have lower levels of this neurotransmitter in their brain. Also, neurons in the gastrointestinal (GI) system use serotonin. The scientists have published their findings in the journal Gastroenterology. Firstly, they wanted to understand whether reducing the level of serotonin in the guts of mice might induce constipation. To investigate, they used a mouse model of depression (MDEP) — these mice have a gene mutation that researchers have linked with severe depression in humans. The mutation reduces levels of serotonin production by 60–80% and induces depression-like behaviors in mice. Reducing serotonin in the gut had several effects; the scientists showed that it lowered the overall number of neurons, caused the gut lining to deteriorate, and reduced the speed of movement through the gut. Dr. Margolis explains, “Basically, the mice were constipated, and they showed the same kind of GI changes we see in people with constipation.”