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Depression And Digestion: The Mysteries Of The Emotional-Gut Connection

What is depression?

Depression is a serious mental disorder characterized by a prolonged period of low mood, loss of interest in favorite activities, changes in energy balance, and a decreased sense of satisfaction with life. It affects overall physical and emotional well-being, the ability to function in daily life, and the quality of interpersonal relationships.

Depression can have different degrees of severity, and without timely treatment, it can become chronic and negatively impact the quality of life. However, depression can also be a symptom of other medical or psychological conditions. Distinguishing between depression as a symptom and depression as a standalone condition is usually based on the duration, frequency, severity of symptoms, and their impact on daily life.

How to identify depression as a symptom of another condition?

Depression as a symptom:

  • Associated with another condition: for example, depressive symptoms may be part of anxiety disorders, seasonal affective disorder, anemia, etc.
  • Limited in time: depressive symptoms may manifest in specific situations, during stress, or in periods of life changes.
  • Disappears with the treatment of the underlying condition: when the primary illness is under control, depression symptoms may decrease or disappear altogether.

Now, let’s consider another scenario – depression as a standalone condition unaffected by other problems.

Depression as a standalone condition:

  • Duration of symptoms: depressive symptoms persist for a significant period, typically at least two weeks. However, chronic illnesses may also lead to a similar situation.
  • Frequency and recurrence: depression symptoms manifest not only in response to specific events but occur repeatedly in various situations. Stress can also lead to depressive symptoms, even if it’s just a symptom of another problem.
  • Impact on functioning: depression significantly affects daily life, productivity, relationships, and other areas. The same can be said for depression as a symptom.
  • Personal or family history of depression: if an individual or their relatives have had episodes of depression before, it may indicate a predisposition to this condition. However, several problems where depression is only a symptom also have a genetic predisposition. Of course, it could be a hereditary issue; it’s just that the problem hasn’t been diagnosed in other family members.

Problems That Can Manifest Symptoms Resembling Depression:

All the problems listed below are conditions in which depression is a symptom.

  • Celiac Disease or Non-Celiac Gluten Sensitivity: An autoimmune disease caused by gluten intolerance that can affect mental health.
  • H. pylori Infection: Causes inflammation of the stomach lining. It may be associated with changes in serotonin and other neurotransmitters, affecting mental health.
  • Hypothyroidism: Reduced thyroid function can lead to fatigue, apathy, and mood changes.
  • Hyperthyroidism: Increased thyroid function that can cause anxiety, irritability, and nervousness.
  • Anemia: Iron deficiency can cause fatigue and depression.
  • Diabetes: Elevated blood sugar levels can affect mood and emotional well-being.
  • Viral Infections: Some viruses, such as the Epstein-Barr virus, can cause fatigue and depressive symptoms.
  • Heart Diseases: Issues with the heart can be accompanied by fatigue and mood changes.
  • Chronic Fatigue Syndrome: Characterized by constant fatigue and physical symptoms.
  • Chronic Pain: Long-term pain can affect mental well-being.
  • Seasonal Affective Disorder (SAD): Depressive symptoms associated with seasonal changes.
  • Substance Abuse: Alcohol or drug use can induce depressive symptoms.
  • Neurological Disorders: Diseases such as Parkinson’s or Alzheimer’s can affect mental health.
  • Irritable Bowel Syndrome (IBS): Can cause physical and emotional symptoms.
  • Vitamin D Deficiency: Can negatively impact mood.
  • Vitamin B12 Deficiency: Necessary for the normal functioning of the nervous system. Its deficiency can cause fatigue, weakness, insomnia, and mood changes, including depressive symptoms.
  • Inflammatory Bowel Diseases (IBD): Including Crohn’s disease and ulcerative colitis, characterized by chronic inflammation of the intestines. This condition may be accompanied by abdominal pain, digestive disturbances, weight loss, and fatigue. Emotional states during this can include the onset of depressive symptoms.

It would be logical to assume that since depression cannot be tested with any tests, everything that can be confirmed or refuted using tests and may have similar symptoms should be examined before diagnosing depression, right? I don’t want to generalize, but in my situation, nothing was tested; I was simply prescribed an antidepressant.

My Personal Depression Story:

I tell this story over and over; it has been over 20 years since I was prescribed an antidepressant after just 15 minutes. It took me 6 years to completely wean off any antidepressants, and stories like mine continue to happen.

After childbirth, I developed insomnia. Without much thought, the doctor gave me pills to “sleep better.” At that time, I knew nothing about antidepressants or how difficult it is to stop taking them once you start. I thought these pills would simply help me sleep better because all the natural remedies I had tried until then had no effect. I was a mother of a 4-month-old baby and just wanted to finally get some sleep.

The medication worked wonderfully; I started to fall asleep easily. The dose was low, and it had no side effects. Then the doctor suggested I stop taking the medication since the dose was low, she said, and nothing would happen. I stopped taking the drug, and after 2 weeks, I experienced a full set of withdrawal symptoms: dizziness, vomiting, inability to look at light, and more. I took a taxi to see the doctor, and the driver stopped the car somewhere in the middle of the road because I started vomiting. I felt very ill, as if I were dying. After this episode, the doctor told me that it meant I could never live without an antidepressant, and I needed to go back to it.

It took a year and a half for me to figure out what was what and switch from a prescription antidepressant to a natural one – St. John’s Wort, to be precise. However, not just any St. John’s Wort, but a specially standardized extract from it. It was not an easy journey; the first attempt ended disastrously – I ended up in the hospital by ambulance with a suspected heart attack. The symptoms mimicked a heart attack, but it was the same withdrawal syndrome. The second attempt was successful; I already knew how to adjust the dose of St. John’s Wort and understood that the quality of the supplement was crucial for a successful replacement of the medication.

Six more years passed, and I embarked on a diet that we used for my child – gluten and casein-free. After 8 months on this diet, I easily gave up St. John’s Wort. It turned out I had gluten intolerance, which was hindering neurotransmitter production. In my case, depression was a symptom, not the main issue, but no one checked if I had any problems causing this symptom; I was simply prescribed an antidepressant.

Now, let’s discuss why this happened to me and why this story is quite typical.

What are Neurotransmitters?

Neurotransmitters are chemical substances that play a key role in transmitting signals between nerve cells, or neurons, in the central nervous system. They regulate various physiological and psychological functions, such as mood, sleep, appetite, attention, and other aspects of behavior. Neurotransmitters perform their function in synapses, the points of contact between neurons. When a nerve impulse reaches the end of a neuron (axon), neurotransmitters are released into the synaptic cleft, where they bind to receptors on the surface of another neuron, transmitting the signal. The regulation of these neurotransmitters plays a crucial role in maintaining the balance and normal functioning of the brain. Imbalances can be associated with the onset of depressive symptoms.

In the context of depression, the following neurotransmitters are particularly important:

  • Serotonin: This neurotransmitter, associated with mood, sleep, and appetite regulation, is primarily produced in specialized cells in the gastrointestinal tract. About 90% of all serotonin in the body is concentrated in the intestines. Changes in serotonin levels can affect emotional states. Amino acids tryptophan and 5-hydroxytryptophan are required for its production.
  • Norepinephrine and Dopamine: These neurotransmitters, responsible for mood and energy regulation, are synthesized in nerve cells using the amino acids phenylalanine and tyrosine. Nervous connections and dopamine receptors are also present in the stomach and intestines. Norepinephrine plays a role in regulating intestinal movements and gastric juice secretion.

Modern Understanding of Depression’s Origin:

The main theory of depression’s onset is related to the imbalance of neurotransmitters, such as serotonin, norepinephrine, and dopamine, in the central nervous system. This theory is known as the “monoamine theory.” It assumes that reduced levels of these neurotransmitters can affect mood and cause depressive symptoms.

Key aspects of this theory include:

  • Decreased serotonin levels: Serotonin is a neurotransmitter that regulates mood, sleep, appetite, and other aspects of behavior. Reduced serotonin levels are believed to be associated with the onset of depression.
  • Other neurotransmitters: Norepinephrine and dopamine are also crucial in the brain. An imbalance in them can also affect emotional states and cause depressive symptoms.
  • Genetic influence: Genetic factors may influence a predisposition to depression, including genetic vulnerability to neurotransmitter metabolism disorders.
  • Stress and trauma: Stressors and psychological traumas can exacerbate neurotransmitter imbalances and contribute to the development of depression.

However, in recent years, research on the neurobiology of depression has become more complex, considering changes in brain structure and function, inflammatory processes, and genetic mechanisms.

How Modern Antidepressants Work:

Now, let’s talk a bit about modern medications commonly prescribed for depression. The most modern antidepressants, selective serotonin reuptake inhibitors (SSRIs), affect the serotonin neurotransmission system by increasing the concentration of this neurotransmitter in the synaptic cleft. They act by preventing the reuptake of serotonin back into the neuron, leading to increased availability of serotonin for postsynaptic receptors.

This is generally considered a key mechanism contributing to mood improvement and the reduction of depressive symptoms. It’s important to note that antidepressants do not directly stimulate the production of serotonin in the body; they delay its reuptake into the neuron, enhancing its effectiveness on neuronal receptors.

Increasing the dose of an antidepressant affects its ability to delay the reuptake of serotonin in neurons, thereby increasing the concentration of serotonin in the synaptic cleft.

Note that antidepressants do not increase the synthesis of serotonin itself; they optimize the utilization of the serotonin that has already been produced. Thus, even with an increased dose of an antidepressant, the body still needs to continue producing this neurotransmitter to ensure its presence in the neurotransmission system. If, for some reason, serotonin is not produced, no changes in the antidepressant dose can help raise its level in the synaptic cleft.

Now, remember where 90% of serotonin is produced: in the intestines.

Do you think the presence of an inflammatory process in the intestines will affect the production of serotonin? Let’s see what science says about this.

Overview of the Physiological Connection Between the Brain and the Intestines (Brain-Gut Axis):

The brain-gut axis is a complex system of interaction between the central nervous system (the brain) and the digestive system (the intestines). This connection occurs through neurotransmitters, nerve pathways, and hormones, facilitating the interaction between physiological and emotional aspects.

Key elements in the brain-gut axis include the vagus nerve, which plays a role in transmitting signals between the brain and the digestive organs, and the enteric nervous system, sometimes called the “second brain,” located within the walls of the intestines. These components form a complex feedback system, regulating processes such as food digestion, intestinal motility, and the secretion of hormones and neurotransmitters.

The Connection of Depression with Digestive Disorders:

After all that has been said, it should not surprise you that there is a profound connection between physiological conditions in the body and the development of depression. Digestive disorders can have a direct impact on mental health.

These physiological conditions can affect the levels of neurotransmitters, especially serotonin, which plays a crucial role in mood regulation. Inflammation in the intestines, dysbiosis, and other changes in the gut can influence the brain through the brain-gut axis, affecting emotional states.

The Influence of Digestion on Neurotransmitter Production

The process of absorbing and forming neurotransmitters begins with a proper diet and digestion. Let’s explore potential issues at each stage and factors that may affect the absorption of nutrients:

Chewing: Problems may arise with insufficient chewing, leading to larger food particles entering the stomach, where they will be more challenging to digest.

Stomach: Inadequate secretion of gastric juice or unregulated acidity can hinder the breakdown of proteins by pepsin.

In some cases, gastrointestinal issues may be associated with Helicobacter pylori infection. This bacterium, residing in the stomach’s mucous membrane, is known for its ability to increase acidity in the internal environment.

  • Increased acidity, in turn, can cause alterations in the function of the digestive system.

Inflammation-induced by Helicobacter pylori can affect the activity of digestive enzymes and slow down gastric motility, making the digestion and absorption of nutrients more challenging.

Small Intestine: Imbalanced gut microflora can lead to issues with nutrient absorption. For instance, dysbiosis can reduce the efficiency of absorption.

  • Disruptions in pancreatic or liver function can impact enzyme production, hindering the breakdown of proteins, fats, and carbohydrates.
  • Issues with acidity regulation in the small intestine may affect the efficiency of enzyme function and nutrient absorption.

Microflora: Insufficient intake of prebiotics and probiotics in the diet may affect the composition of the intestinal microflora.

  • Imbalances in the microbiota can trigger inflammatory processes, subsequently influencing the absorption of nutrients.

General Factors: Stress and an unhealthy lifestyle can negatively impact the entire digestive process.

What is crucial for neurotransmitter synthesis?

The regulation of the production of each neurotransmitter involves complex biochemical pathways dependent on the availability of necessary raw materials and enzymes.

  • Amino Acid Deficiency: Amino acids such as tryptophan and tyrosine are fundamental building blocks for neurotransmitter synthesis, including serotonin, dopamine, and norepinephrine.
  • Vitamin and Mineral Deficiency: B-group vitamins (B6, B9, B12), vitamin C, magnesium, zinc, and other trace elements play roles in various phases of neurotransmitter synthesis.
  • Deficiency in Fat-Soluble Substances: Omega-3 fatty acids and other fat-soluble substances can influence brain function and neurotransmitter activity.
  • Hormonal Imbalances: Excess or deficiency of certain hormones, such as insulin, can affect processes regulating neurotransmitter synthesis.
  • Reduced Antioxidant Efficiency: Antioxidant deficiency may increase oxidative stress and damage neurotransmitters.
  • Inadequate Hydration: Water deficiency can reduce the efficiency of metabolic processes, including neurotransmitter synthesis.

Therapies and Activities Influencing Neurotransmitter Production

To increase serotonin levels, the following recommendations can be applied:

  • Sunlight: Sunlight stimulates serotonin production. Try spending more time outdoors, especially during periods of solar activity.
  • Physical Activity: Regular physical exercises, particularly aerobic exercises, can contribute to increased serotonin and other neurotransmitter levels.
  • Stress and Environment: High-stress levels, adverse environmental conditions, or an imbalanced lifestyle can negatively affect neurotransmitter synthesis.
  • Relaxation Exercises: Incorporate relaxation methods such as meditation, deep breathing, and yoga into your routine. These practices can reduce stress levels and improve neurotransmitter balance.
  • Positive Social Interactions: Social support and positive interactions with loved ones can significantly impact emotional well-being and neurotransmitter balance.


As evident from the foregoing discussion, there are numerous factors capable of triggering symptoms of depression. Professionals who demonstrate a willingness not only to alleviate the consequences of depression but also to identify its root causes play a pivotal role in this process. This approach emphasizes the importance of not just alleviating symptoms but also seeking fundamental solutions.

Moreover, symptoms can often be improved even before the fundamental cause is identified, and this doesn’t always necessitate pharmacological antidepressants. When symptoms of depression arise, seeking help from professionals is always recommended. Even professionals specializing in this field often seek advice from colleagues because mental health impedes an objective view of one’s problems.