Series: The source of emotions lies in "gut bacteria"

Series: The Source of Emotion Lies in the Gut, Part 1

Why Emotions Are Not Created by the Brain Alone

Rethinking “Mental Health” and School Refusal Through the Gut-Brain Axis

When people feel emotionally unwell and say things like, “I have no motivation,” or “I feel vaguely anxious,” they tend to assume that the problem must be in the brain.

However, recent research on the gut-brain axis suggests that emotions, stress responses, and behavioral tendencies may be shaped not only by the brain, but also by interactions among the gut microbiota, the immune system, metabolism, and neural pathways [3][4][5][6].

At the same time, the latest statistics from Japan’s Ministry of Education show that the number of children refusing school remains at a record high, and that factors such as apathy, anxiety, disrupted daily rhythms, and sleep deprivation often overlap in the background [1].For that reason, when we think about a child’s emotional distress or school refusal, it is important to look not only at school or family issues, but at the broader picture, including sleep, diet, physical condition, and the digital environment [1][2][7][8].

1. The Gut Microbiota Is an Important Regulatory System Separate From the Brain

The human brain is thought to contain roughly 86 billion neurons.By contrast, the gut contains a vast community of microorganisms that are known to influence metabolism, immune activity, and pathways related to neurotransmitters [3][4][5].

The key point here is not to oversimplify and say that “emotions are created only in the gut,” but rather to understand that the gut is one of the major organs involved in emotional regulation [3][4][6].In other words, if we look only at the brain, we may miss the full picture of a child’s distress.

2. Serotonin and the Deep Connection Between the Gut and Emotional Stability

Serotonin, often called the “happiness hormone,” is a neurotransmitter involved in emotional stability and mood regulation.Recent studies have shown that much of the body’s serotonin is produced in the digestive tract, especially in enterochromaffin cells in the gut [4][9][10].

At the same time, it is important not to misunderstand this point.Serotonin produced in the gut does not simply travel directly into the brain.Communication between the gut and the brain is thought to involve multiple pathways, including tryptophan metabolism, the vagus nerve, immune signaling, and short-chain fatty acids [4][9][10][11].

This means that when the gut environment becomes disturbed, the problem is not limited to the digestive system alone.It may also affect the quality of signaling being sent to the brain [3][4][5].

3. What Germ-Free Mouse Studies Suggest About the Relationship Between the Gut and Behavior

One of the most well-known lines of research showing that gut bacteria may influence behavior and stress responses comes from studies using germ-free mice [12][13].These studies found changes in anxiety-like behavior, social behavior, and brain neurochemistry, suggesting that the gut microbiota may play a role in brain development and behavior [12][13][14][15].

Still, caution is necessary here.The results of germ-free mouse studies cannot be directly applied to human school refusal or emotional disorders.Even so, they remain biologically important foundational studies showing that the gut environment is not unrelated to the brain or behavior [3][6][14].

This perspective becomes especially relevant when considering conditions commonly seen in children today, such as apathy, difficulty concentrating, impulsivity, and disrupted sleep rhythms.

4. To Understand School Refusal, We Need to Look at the Whole Body, Not “Brain or Gut”

School refusal does not have a single cause.The Ministry of Education’s own surveys indicate that apathy, anxiety, school-related stress, family issues, and disrupted life routines often overlap in the background [1].

In addition, a growing body of research shows that excessive smartphone and internet use is associated with sleep problems, anxiety, and depression [7][8][16][17][18].Japan’s Ministry of Health sleep guidelines also make clear that nighttime use of digital devices can affect sleep habits [2].

For this reason, it is not helpful to frame the issue as a simple choice between “the brain is the problem” or “the gut is the problem.”What matters is looking at the gut-brain axis, sleep, daily rhythms, diet, exercise, stress, school context, and family environment together as one integrated system [1][2][3][4][7][8].

5. Regulating Emotions Means Regulating Daily Life as a Whole

What we call “emotion” is not an isolated event that appears suddenly in the brain.It shifts under the influence of physical condition, sleep, food, gut health, stress, and human relationships [3][4][5][6].

From this perspective, supporting school refusal or emotional distress cannot mean reducing everything to “a matter of feelings.”What is needed is a combination of restoring healthy routines, rebuilding sleep, stabilizing the body, creating safe relationships, and providing psychosocial support when necessary [1][2][7][8][26].

Improving the gut environment may be one meaningful part of that process.However, it should not be oversimplified, because gut health alone does not solve everything [6][23][24][25][26].

6. BDNF and Exercise Are Important Pathways That May Support Recovery

BDNF, or brain-derived neurotrophic factor, has attracted attention as a molecule related to brain recovery and plasticity.Recent reviews consistently suggest that exercise may increase BDNF levels, and more studies now support this connection even in adolescents and young people [19][20][21][22].

This suggests that when thinking about recovery support for school refusal or apathy, not only diet but also light aerobic exercise and physical activity may have neurobiological significance [19][20][22].

At the same time, it is important not to treat BDNF as “the one and only key.”Exercise is one promising support strategy, but in reality it is most effective when combined with sleep, nutrition, interpersonal support, and psychological safety [19][20][21].

7. Conclusion

The Mind Is Supported Not Only by the Brain, but by the Entire Body’s Network

Current gut-brain axis research suggests that our emotions and behaviors may be shaped not only by the brain, but also by interactions among the gut microbiota, the immune system, metabolism, sleep, lifestyle, the digital environment, and the social environment [3][4][5][6][7][8].

That is why, when facing school refusal or emotional distress, it is not accurate to blame “the child’s weak will” or “poor parenting” [1][7][8].

To understand a child’s distress, we need to look not only at the brain, but also at the gut, sleep, lifestyle, and social environment.And the path to recovery is not a single road.It lies in combining multiple forms of support from multiple angles [1][2][6][19][26].

References

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