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Why I See Depression As A Symptom — Not A Diagnosis

Daniel Amen, M.D.
May 30, 2023
Daniel Amen, M.D.
Clinical neuroscientist psychiatrist
By Daniel Amen, M.D.
Clinical neuroscientist psychiatrist
Daniel Amen, MD, is a clinical neuroscientist psychiatrist, physician, professor and 10-time New York Times bestselling author. He is a double board-certified child and adult psychiatrist and founder of Amen Clinics, Inc.
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Image by Lucas Ottone / Stocksy
May 30, 2023

People are always surprised when they hear me—a psychiatrist for more than 40 years—say that I don't like the diagnosis of depression.

Why do I say that? Imagine if you had crushing chest pain and you went to see your cardiologist and they simply gave you a diagnosis of chest pain. The problem is that it doesn't tell you what's causing your symptoms or what to do about it. With depression, it's the same thing.

Being diagnosed with depression doesn't indicate the root cause of your depressive symptoms, and it doesn't help target treatment. It's part of the reason treatment-resistant depression is so common. One randomized controlled trial1 found that over half of depressed people don't experience relief from symptoms when treated with antidepressants. Even worse, about one in three individuals with depression fail to achieve remission following four courses of antidepressant treatment.

Treatment failures are far too common, in large part because depression isn't a single or simple disorder. There are many possible causes of depression. Some of the most common biological factors that I see contribute to depression include:


Low thyroid levels

An underactive thyroid can make you feel sluggish, and decades of research show that it is linked to depression. According to a 2022 review, hypothyroidism is one of the primary underlying causes of treatment-resistant depression2. Low thyroid also impacts brain function.

At Amen Clinics, we use a brain imaging technology called SPECT to look at the brains of our patients. SPECT measures blood flow and activity. On brain SPECT scans, low thyroid levels are associated with overall low activity in the brain, which we also see in patients with brain fog and depression.

The fix

Treating hypothyroidism can be highly beneficial in enhancing moods, so get your thyroid levels checked and optimize them if needed. Natural ways to support thyroid health include cutting sugar out of your diet, eating foods high in selenium (such as tuna, turkey, and Brazil nuts), and taking vitamin B-12.

Exposure to mold

Living in a moldy home or working in an office where mold is present can dampen your mood. Research from Brown University involving nearly 6,000 people found a strong connection between mold and depression

The fix

Remove yourself from the moldy environment, if possible, and call a mold remediator. To prevent mold from forming, always fix water leaks and plumbing problems immediately, and use air purifiers. Treatment for brain toxicity may include binding agents, medications, metabolic support supplements, and more. Talk with your doctor if you suspect you've been exposed to mold.

Heart disease

Growing up, my best friend was my grandfather, who was always smiling and happy. He was a candy-maker, and some of my best memories are of making fudge with him. But all that candy took a toll, and at age 69, he had a heart attack. After that, everything changed. He cried a lot, seemed unhappy, couldn't sleep, and was eventually diagnosed with depression. I didn't know it at the time, but depression is three times more common in people following a heart attack, according to research.

The fix

Get serious about heart health and if you have heart disease, pay attention to your emotional well-being. Practice self-care and follow your health care provider's recommendations for diet and exercise. Joining a support group can also be a therapeutic outlet, as a 2023 study found that having strong social bonds is associated with less depression.

Head injuries

Mild traumatic brain injuries—even ones that don't cause you to black out or don't get diagnosed as a concussion—can change your life in so many ways. Depression is just one of them. According to a 2020 study in Frontiers in Neurology, people with a history of a mild head injury are over three times as likely to have depression3 compared with individuals who have not experienced head trauma.

In about 40% of our patients at Amen Clinics, the brain scans show evidence of previous head trauma.

In about 40% of our patients at Amen Clinics, the brain scans show evidence of previous head trauma. Surprisingly, many of those patients either don't remember getting injured or think their injury was so minor it wasn't worth mentioning. They would never make the connection between their current depressive symptoms and falling off a bike as a kid or getting in a fender bender as a teen.

The fix

Healing the underlying brain trauma is one of the keys to achieving happier, more positive moods. Hyperbaric oxygen therapy (HBOT) has been shown to accelerate the healing process in people with head injuries. One study in the Journal of Neurotrauma found that one single session of HBOT increased blood flow to the brain in people with mild to moderate TBI.


A silent cause of depression, chronic inflammation ravages the body, the brain, and the mind. A number of studies point to high levels of inflammation as a risk factor for a variety of mental health issues, including depression, anxiety disorders, bipolar disorder, and more.

The fix

Because poor gut health is strongly associated with elevated levels of inflammation, be good to your gut by taking a high-quality probiotic supplement. Scientific evidence shows that certain nutritional supplements that have anti-inflammatory properties—such as omega-3 fatty acids and curcumin—have been found to decrease depression in individuals with chronic inflammation.


Infections are a major cause of psychiatric disorders, such as depression, but few people know it. In particular, a significant number of people are experiencing depressive symptoms post-COVID. A 2021 study in JAMA Network Open found that 52.4% of post-COVID patients met the criteria for major depressive disorder4 several months after being infected.

The brain imaging work at Amen Clinics shows that having COVID is associated with increased activity in the limbic system (emotional centers) of the brain. This is a common brain activity pattern also seen in people with depression. 

The fix

Boost your immune system with nutritional supplements like vitamin D and therapeutic mushrooms (such as Lion's mane and reishi). Eat foods that have immune-boosting properties, including garlic and onion. In addition, emerging science shows that infrared sauna therapy may be helpful in healing from infections like COVID and shows promise as a treatment for depression. And take note that overcoming long COVID may require a complete brain-body approach that includes lifestyle changes, psychological strategies, and more.

The takeaway

It's clear that depression can be a complex disorder with multiple causes. That's why it's so important to undergo comprehensive testing to determine the root cause or causes of your depression. Only by addressing all of the underlying causes can you truly heal from this potentially debilitating condition so you can start feeling happier and more positive.

Daniel Amen, M.D. author page.
Daniel Amen, M.D.
Clinical neuroscientist psychiatrist

Daniel Amen, MD, is a clinical neuroscientist psychiatrist, physician, professor and 10-time New York Times bestselling author. He is a double board-certified child and adult psychiatrist and founder of Amen Clinics, Inc., which has eight clinics across the country with one of the highest published success rates for treating complex psychiatric issues with the world’s largest database of functional brain scans relating to behavior, with more than 160,000 scans on patients from 121 countries. Amen is the lead researcher for the largest brain imaging and rehabilitation study for professional football players that demonstrates high levels of brain damage in players with solutions for significant recovery as a result of his extensive work. His research on post-traumatic stress disorder and traumatic brain injury was recognized by Discover magazine’s Year in Science issue as one of the “100 Top Stories of 2015.” Amen has authored and co-authored more than 70 professional articles, seven scientific book chapters and 40-plus books, including the No. 1 New York Times bestsellers, “The Daniel Plan” and “Change Your Brain, Change Your Life.” His most recent book, “Change Your Brain, Change Your Grades,” includes editorial contributions from his teenage daughter, Chloe Amen, and niece, Alizé Castellanos.