Does an Imbalanced Gut Affect Mental Health?

New Research Links Gut Health, Autoimmune Diseases, Allergies, and Depression Risk

It has become increasingly clear that the gut environment plays a critical role in both physical and mental health.

Approximately 60–70% of the human immune system—including immune cells and antibodies—is located in the gut. When the gut microbiome becomes imbalanced, harmful bacteria may increase while beneficial bacteria decline, potentially weakening immune function. This imbalance has been associated with a range of physical symptoms, as well as low mood, fatigue, and reduced motivation.

If gut imbalance persists over time, immune dysfunction may escalate from simple weakening to immune overactivation. This immune dysregulation has been linked to the development of allergic conditions, autoimmune diseases, and mental health disorders such as depression.

When the immune system becomes overactive, it may trigger allergic conditions such as hay fever, atopic dermatitis, and food allergies, as well as autoimmune diseases.

Autoimmune diseases occur when immune cells mistakenly attack the body’s own healthy tissues. Common examples include rheumatoid arthritis, inflammatory bowel disease (IBD), Graves’ disease, Hashimoto’s thyroiditis, systemic lupus erythematosus, and multiple sclerosis.

Autoimmune Diseases and Mental Health Risk: Large-Scale Evidence

A research group from the University of Edinburgh’s Centre for Clinical Brain Sciences investigated the association between autoimmune diseases and mental health disorders. Their findings were published in BMJ Mental Health on June 10, 2025.

According to the study, individuals with autoimmune diseases had approximately twice the risk of developing mental health disorders—such as depression, anxiety disorders, and bipolar disorder—compared with the general population. The association was more pronounced in women than in men.

Study Population and Design

This analysis used data from “Our Future Health,” a newly established large-scale UK cohort study. The study included 1,563,155 adults aged 18 and older who self-reported their physical and mental health histories.

Six autoimmune diseases were examined: rheumatoid arthritis, Graves’ disease, inflammatory bowel disease (IBD), systemic lupus erythematosus, multiple sclerosis, and psoriasis.

Participants were divided into two groups:

• Autoimmune disease group: 37,808 individuals
• General population group: 1,525,347 individuals

Key Findings

The lifetime prevalence of mental health disorders—including depression, anxiety disorders, and bipolar disorder—was 28.8% among individuals with autoimmune diseases, compared with 17.9% in the general population.

Depression prevalence was significantly higher in the autoimmune group:

• 25.5% in individuals with autoimmune diseases
• 15.2% in the general population

Unit of meassurement	General Population	Patients with Autoimmune Diseases
Lifetime Incidence of Mental Disorders	17.9%	28.8%
Lifetime Prevalence of Depression	15.2 %	25.5 %
Prevalence of Depression (at the Time of Survey)	10.5 %	18.6 %
Anxiety Symptoms	12.9 %	19.9 %

At the time of assessment, active depressive symptoms were observed in 18.6% of individuals with autoimmune diseases, compared with 10.5% in the general population.

Anxiety symptoms followed a similar pattern:

• 19.9% in the autoimmune group
• 12.9% in the general population

。

Gender	Prevalence of Mental Disorders
Male	20.7%
Female	31.6%

The authors suggest that chronic inflammation associated with autoimmune diseases may amplify immune-to-brain signaling, increasing vulnerability to mental health disorders. They also note that differences in sex hormones, chromosomes, and immune antibody responses may partially explain the higher prevalence in women.

Supporting Mental and Immune Health Through Diet

Maintaining a healthy gut environment may contribute not only to immune balance but also to mental well-being.

In addition to regular sleep, stress management, and consistent daily routines, dietary choices play a central role. Diets rich in dietary fiber—such as legumes, whole grains, and vegetables—are particularly important for gut health.

Fermented foods such as natto, miso, pickled vegetables (including kimchi and rice-bran pickles), and yogurt are especially noteworthy. These foods provide nutrients in more absorbable forms and supply beneficial bacteria directly, along with fiber and bioactive compounds that support gut microbiome diversity.

Incorporating fermented foods into daily meals may be a practical way to support both physical and mental health in the long term.

Summary

Recent large-scale research indicates that autoimmune diseases are associated with a significantly higher risk of depression and anxiety. Because gut health is closely tied to immune regulation, maintaining a balanced gut environment—through diet and lifestyle—may play an important role in supporting mental well-being.

参考文献

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