A new U.S. study has found that people with poor chewing ability and symptoms of depression are more likely to experience constipation. When these two conditions occur together, the risk of constipation is even higher.
The research used health data from 10,814 adults collected between 2005 and 2010 as part of the National Health and Nutrition Examination Survey (NHANES).
Poor Oral Health and Depression Each Raise Risk
The researchers focused on two key factors: chewing ability and depression. Chewing ability was measured by the number of functional tooth units (FTUs), which are pairs of opposing back teeth that help grind food. Fewer FTUs meant poorer chewing capacity. Participants were grouped into three categories: 10–12 FTUs, 3–9 FTUs, and 3 or fewer FTUs.
Depression was measured using a common screening tool called the PHQ-9. A score of 10 or higher indicated moderate to severe depression.
Constipation was identified based on self-reported stool consistency and frequency. Participants were considered constipated if their stools were hard and lumpy or if they had fewer than three bowel movements per week.
Key Findings
The study found that:
People with better chewing function (10–12 FTUs) had the lowest risk of constipation.
Depression was linked to a nearly twofold higher chance of constipation (Odds Ratio [OR] = 1.94).
Those with both poor chewing (≤3 FTUs) and depression had the highest constipation risk (OR = 2.36).
Importantly, the researchers discovered that depression partly explained why people with poor chewing ability were more likely to have constipation. This suggests a biological or behavioral link between oral health and mental health in digestive function.
What This Means
The study highlights the importance of both oral and mental health in preventing constipation. Researchers recommend that health providers pay attention to dental care and emotional well-being when treating people with gastrointestinal issues.
The findings support the idea that improving chewing ability—such as with dentures or implants—and addressing depression may help reduce constipation symptoms, especially in older or medically vulnerable populations.
Why Chewing and Mood Matter for Digestion
Constipation is a widespread digestive issue often caused by poor diet, lack of exercise, or medication. But recent studies have shown that chewing difficulties and mental health also play a role.
Poor chewing can lead to changes in diet, especially lower fiber intake, which slows digestion. Depression affects the gut-brain axis—how the brain and gut communicate—potentially leading to slower bowel movements.
While past studies have looked at chewing or depression separately, this is one of the first to examine their combined impact on constipation.
Study Details
Participants came from NHANES, a U.S. health survey that collects information on diet, medical conditions, and lifestyle. The research team excluded individuals who were missing key data, ensuring a robust sample size.
FTUs were measured during dental exams by trained professionals. Depression levels were assessed through a self-reported questionnaire. Stool data came from the Bristol Stool Form Scale and bowel movement frequency reports.
To ensure accuracy, researchers adjusted for a wide range of factors, including age, sex, race, education, income, body weight, smoking, alcohol use, and chronic conditions like diabetes and heart disease.
Some dietary and physical activity data were not included due to missing or inconsistent records.
Conclusion
This study shows that chewing ability and depression both influence constipation risk—and that they may work together to make the problem worse.
Improving dental health and treating depression could be effective ways to reduce constipation, especially for those who struggle with both issues.
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