Why Antidepressants Work for Some—but Fail for Others

Depression may not be a single disorder with a one-size-fits-all treatment protocol.

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For decades, depression has been treated largely as a single condition. Yet anyone who has struggled with depression—or cared for someone who has—knows that no two cases look exactly alike. Some people respond well to antidepressants, while others experience little relief despite trying multiple medications and therapies.

According to researcher William J. Walsh, one reason may be that depression is not a single illness at all.

In an interview on “Vital Signs” with host Brendon Fallon, Walsh said that what is commonly labeled depression may actually encompass several distinct biochemical disorders, each involving different nutrient imbalances, neurotransmitter patterns, and treatment needs. If true, this could help explain why treatments that work remarkably well for some patients fail to help others.

After more than four decades of research and clinical work, Walsh said he believes that the future of mental healthcare lies in identifying the biological factors driving each individual’s symptoms and tailoring treatment accordingly.

Why Depression Treatment Doesn’t Work the Same for Everyone

Depression is typically diagnosed based on symptoms such as persistent sadness, loss of interest, fatigue, changes in sleep, and difficulty concentrating. While this symptom-based approach helps clinicians identify the disorder, it may not reveal its cause.

“Two people can have nearly identical symptoms but very different underlying biochemistry,” Walsh said.

This idea is increasingly reflected in modern medicine. In fields ranging from oncology to cardiology, researchers have discovered that diseases once thought to be single conditions often consist of multiple subtypes, each requiring a different treatment approach. Mental health researchers are now exploring whether depression may follow a similar pattern.

Rather than viewing depression as one disease, Walsh describes it as an umbrella diagnosis that includes several biologically distinct disorders.

5 Biochemical Patterns Behind Depression

Based on decades of biochemical testing and clinical observations, Walsh has identified five major patterns commonly seen among people diagnosed with depression.

1. Undermethylation

According to Walsh, undermethylation is one of the most common biochemical patterns among people with depression.

Methylation is a fundamental biochemical process involved in regulating gene activity, producing neurotransmitters, repairing cells, and maintaining normal brain function. When methylation is impaired, neurotransmitter balance may be affected.

Walsh noted that people in this group often exhibit perfectionistic tendencies, strong achievement orientation, and a heightened susceptibility to depressive symptoms.

2. Overmethylation

At the opposite end of the spectrum is overmethylation.

Although less widely recognized, Walsh said he believes this biochemical pattern can also contribute to depression, anxiety, panic attacks, and emotional sensitivity.

Importantly, he said, interventions helpful for undermethylated individuals may be inappropriate—or even counterproductive—for those who are overmethylated.

3. Copper Overload

Another pattern involves elevated copper levels.

Copper is an essential mineral that plays important roles in energy production, nervous system function, and connective tissue formation. However, Walsh said he believes that excessive copper accumulation may disrupt neurotransmitter activity and contribute to mood disorders.

He has observed associations between copper overload and symptoms such as anxiety, mood instability, irritability, and postpartum depression.

4. Pyroluria

Pyroluria is a condition that Walsh associates with abnormal losses of zinc and vitamin B6, two nutrients essential for healthy brain function.

According to his clinical observations, those with this pattern may experience emotional sensitivity, poor stress tolerance, social anxiety, and mood disturbances.

Although pyroluria remains controversial within mainstream medicine, Walsh considers it an important biochemical factor in some patients.

5. Toxic Overload

Environmental exposures may also play a role.

Heavy metals, chemical pollutants, and other toxic substances can increase oxidative stress and inflammation, potentially affecting brain health and emotional well-being.

Walsh said he believes that identifying and addressing these burdens may be beneficial for selected patients whose symptoms are linked to toxic exposures.

The Hidden Importance of Methylation

Of all the biochemical processes discussed during the interview, methylation received the greatest attention.

Methylation occurs billions of times each day throughout the body and helps regulate numerous biological functions, including:

• Neurotransmitter production
• Gene expression
• Detoxification pathways
• Cellular repair
• Brain development

Because methylation influences the production and activity of neurotransmitters such as serotonin, dopamine, and norepinephrine, abnormalities in this process may have widespread effects on mood and cognition.

Walsh said that understanding a patient’s methylation status may provide important clues about which nutritional or medical interventions are most appropriate.

The concept aligns with a growing body of research suggesting that depression involves far more than serotonin alone. Scientists now recognize that inflammation, metabolism, nutrient status, genetics, immune function, and environmental factors may all contribute to the condition.

The Zinc–Copper Connection

One of Walsh’s most extensively studied areas involves the relationship between zinc and copper.

Both minerals are essential for health, but they must remain in balance.

Zinc participates in hundreds of enzymatic reactions throughout the body and plays important roles in immune function, neurotransmitter activity, and antioxidant defenses. Copper is also necessary, but excessive amounts may alter the activity of neurotransmitters involved in mood regulation.

Walsh has found that some patients with depression and anxiety exhibit elevated copper levels combined with low zinc status. Correcting these imbalances, he said, may help improve symptoms in certain individuals.

While researchers continue to investigate the role of trace minerals in psychiatric disorders, interest in the relationship between nutrition and mental health has grown substantially over the past decade.

Can Nutrients Help Rewire Brain Chemistry?

Walsh’s treatment approach centers on targeted nutrient therapy designed to address specific biochemical abnormalities.

Depending on an individual’s biochemical profile, interventions may include nutrients such as:

• Zinc
• Vitamin B6
• Folate
• Methionine
• Other vitamins, minerals, and amino acids involved in neurotransmitter production

The goal is not simply to supplement deficiencies but to support the body’s ability to produce and regulate brain chemicals more effectively.

During the interview, Walsh reported that approximately 80 percent to 85 percent of depressed patients in his clinical database experienced significant improvement following individualized nutrient-based treatment programs.

However, experts note that such findings largely stem from clinical practice and observational data. Additional large-scale randomized controlled trials are needed to determine how broadly these results apply and which patients are most likely to benefit.

A Shift Toward Personalized Psychiatry

Although some of Walsh’s theories remain subjects of scientific debate, his broader message reflects a growing trend in medicine: personalization.

Researchers increasingly recognize that patients with the same diagnosis may have very different biological profiles. Advances in genetics, biomarker testing, nutritional psychiatry, and precision medicine are helping clinicians move beyond one-size-fits-all approaches.

This shift is especially relevant for depression, a condition that affects an estimated 280 million people worldwide and remains one of the leading causes of disability.

Mainstream psychiatry generally agrees that biology, nutrition, genetics, inflammation, and environmental influences all play roles in mental health. Where researchers continue to differ is in determining which biomarkers are most useful, how they should be measured, and how strongly they should guide treatment decisions.

Looking Beyond the Label

Walsh said he believes that the most important question in mental healthcare may not be whether someone has depression, but why that person has it.

Rather than viewing depression as a single disorder requiring a standard treatment, he envisions a future in which clinicians identify the specific biological factors contributing to each person’s symptoms and develop interventions tailored to those needs.

Whether that future ultimately includes widespread biochemical profiling remains to be seen. However, as scientists continue uncovering the complex biological pathways involved in mood disorders, one thing is becoming increasingly clear: Depression may be far more diverse—and far more individualized—than previously thought.

For patients who have struggled to find answers, that possibility offers both a challenge and a source of hope. Understanding the biology behind depression may eventually lead to treatments that are not only more precise, but also more effective.

To learn how to get tested and treated under the Walsh protocols, watch “Rewiring Depression: 80–85 Percent of Depressives Improve Significantly on Advanced Nutrient Therapy,” featuring William J. Walsh, on EpochTV here.