10 Physical Conditions That Mimic Mental Illness

If you’ve been diagnosed with a mental illness, your condition could have an underlying physical cause. More often than not, when a person presents with the signs of mental illness, they are put on medication to stabilize their condition and relieve their symptoms.

While this may make the person feel better in the short term, it does not address the possible physical causes of the symptoms of mental illness.

Here are 10 physical diseases that mimic mental illness:

1. Gluten Intolerance

Gluten is a protein found in wheat, barley, and rye. If you are intolerant to this protein, you may notice physical symptoms such as chronic abdominal pain, diarrhea, constipation, weight loss or gain, hair loss, and irritable bowel syndrome.

Gluten not only affects the digestive system, it can also have a profoundly negative impact on the nervous system. Neurological symptoms of gluten intolerance include mental dullness, confusion, learning impairments, brain fog, autism spectrum disorder symptoms, anxiety, depression, behavioral problems in children, and, in severe cases, psychosis.


2. Thyroid Disease

Thyroid disease is a common physical condition that mimics the symptoms of mental illness.

In hypothyroidism, the production of the thyroid hormone is insufficient. This can result in mental symptoms such as insomnia, hallucinations, paranoia, emotional instability, suicidal thoughts and actions, nightmares, and depression.

Physical symptoms of hypothyroidism include weight gain, sensitivity to cold, thinning hair, anemia, muscle aches, muscle weakness, and dry skin.

In the case of hyperthyroidism, the thyroid produces too much of the hormone, resulting in nervousness, hyperactivity, mood swings, insomnia, staring gaze, anxiety, and depression.

Physical symptoms of hyperthyroidism include unexplained weight loss, heat intolerance, diarrhea, menstrual irregularities, shaking hands, hair loss, and a fast heart rate.

3. Heavy Metal Toxicity

Exposure to certain heavy metals in the environment can cause the symptoms of mental illness. The most common culprits in heavy metal toxicity are mercury, lead, cadmium, and arsenic.

  • Mercury

Mercury toxicity can occur as a result of mercury fillings, vaccinations, or industrial exposure. Neurological symptoms include muscle twitching, muscular atrophy, mood swings, nervousness, irritability, and decreased cognitive function.

  • Lead

Lead poisoning can be the result of industrial exposure, lead paint exposure, or use of certain cosmetics containing lead. Mental symptoms of lead poisoning include anxiety, delusions, nightmares, and confusion.

  • Cadmium

It may surprise you to know that cadmium can be found in some children’s toys. The most common sign of cadmium toxicity (especially in children) is sudden behavioral abnormalities. It can also cause depressive symptoms in adults.

  • Arsenic

Industrial and food (fish, shellfish) exposure are the most common causes of arsenic toxicity. Arsenic toxicity has been linked to dementia, apathy, and anorexia nervosa.

4.  Lyme Disease

Lyme disease is caused by a bite from an infected tick.

Early physical symptoms include flu-like symptoms, localized rash at the site of the bite, headache, fatigue, and muscle aches. As the disease progresses, symptoms such as facial tics, poor memory and concentration, pain or weakness in the limbs, personality changes, OCD, delusions, paranoia, and fear may present.

If these symptoms sound familiar, get tested for Lyme disease immediately. Left untreated, it can cause permanent physical and neurological damage.

5. Parasites

Research shows that over 50 percent of Americans are infected with at least one type of parasite. The symptoms are so numerous that it can take years of trial-and-error diagnosis before the true cause is found (if it ever is).

Physical symptoms of parasitic infection include chronic diarrhea (which may or may not alternate with constipation), multiple food allergies, appetite changes, excessive and foul-smelling gas, nausea, vomiting, anal itching, dizziness, and heart palpitations.

Mental symptoms include insomnia, waking at odd hours (such as 3 a.m.), anxiety and irritability, brain fog, depression, and poor memory.

6. Chronic Candida Infection

Candida is a type of yeast that lives in the body. In small amounts, it is harmless. When it begins to overgrow and spread throughout the body unchecked, however, it can cause serious illness.

Physical symptoms of chronic candidiasis include recurrent yeast infections, athlete’s foot, gastrointestinal problems, craving for sweets and alcohol, restlessness, acid reflux, low libido, and itching.

Mental symptoms include anxiety, irritability, poor memory, brain fog, mood swings, manic depression, depression, delusions, and psychosis.

7. Vitamin B3 Deficiency (Pellagra)

Although rare in the United States, a person with a vitamin B3 (niacin) deficiency can exhibit physical symptoms such as muscle weakness, red scaly skin, loss of appetite, and diarrhea.

Neurological symptoms can include dizziness, headaches, and mental disturbances.

8. Vitamin B12 (Folic Acid) Deficiency

Folic acid deficiency can occur after surgery that removes part of the intestine. This leads to malabsorption of the nutrient, which can cause physical symptoms such as weakness, pallor, mouth lesions, red, sore tongue, restless legs syndrome, nausea, and vomiting.

Neurological symptoms of folic acid deficiency include moodiness, learning impairment, anxiety, insomnia, poor coordination, mania, hallucinations, paranoia, and psychosis.

9. Hypoglycemia

A person with hypoglycemia has abnormally low blood sugar, which can cause neurological symptoms such as inebriated (drunk) appearance, anxiety, sudden emotional outbursts, and excessive crying.

Physical symptoms include weakness, shakiness, excessive sweating, and loss of consciousness.

10. Histadelia

Histadelia is a condition characterized by too much histamine in the blood. This condition seems to affect men more than women, and research has shown that 15 to 20 percent of people who have been diagnosed with schizophrenia, in fact, have histadelia.


Worried and depressed man isolated on black


Physical symptoms include fast metabolism, excessive sweating, frequent colds, allergies, thin build, and low pain tolerance.


Mental symptoms include strong suicidal tendencies, obsessions, mind blanks, severe depression, hyperactivity, and phobias.


If you believe you have one or more of these conditions, talk with a naturopathic or integrative medicine physician who will give you the proper tests for accurate diagnosis.


Never suddenly stop taking any prescription medication as it could be very hazardous to your health and may even be fatal.


If a physical condition is making it appear as though you have a mental illness, there are plenty of steps you and your healthcare provider can take together to solve the mystery so you can regain your health.


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About Author: Jaime A. Heidel

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