Watch Out! Your Patient’s Depression may be due to a Medical Illness

Our special correspondent Psychiatrist Esther Oh, MD concludes her series on medical illnesses that can cause psychiatric symptoms with a look at depression


Depression is one of the most commonly diagnosed psychiatric disorders, affecting over 18 million Americans each year. Not only is depression associated with an increased risk for diabetes, cardiovascular disease, and delay in recovery from medical illness, it can also be caused by various medical conditions. Why is this important for internists to know? Approximately 50% of patients with a serious psychiatric illness have general medical conditions that are either undiagnosed or untreated and may cause or exacerbate their psychiatric symptoms. Also, 10% of psychiatric symptoms may be the presenting complaint for a medical problem.


What are possible warning signs that depressive symptoms are caused by a medical condition?
  • Onset of symptoms after the age of 40
  • No personal or family history of depression
  • Symptoms that occur during a major illness or flare-up
  • Symptoms correlate with starting a medication
  • Psychiatric symptoms that improve with treatment of a medical illness
  • Using multiple medications
  • Waxing and waning presentation or any acute change in mental status
  • Cortical dysfunction such as dysphagia, apraxia, agnosia
  • Abnormal vital signs, focal neurologic deficits
  • Ocular abnormalities (pupillary changes, nystagmus)
  • Rare hallucinations such as visual, tactile or olfactory hallucinations
To help you organize the extensive list of possible diagnoses, we will group the medical disorders into different categories.


Infectious Diseases
  • Lyme disease
    • Known as a “ great imitator”, this bacterial infection is caused by Borrelia burgdorferi, which is transmitted by the deer tick.
  • Syphilis
    • Also known as a “great imitator”, causes various neuropsychiatric symptoms if left untreated. Symptoms can include irritability, personality changes, and poor self care, similar to depression.
  • Neurocysticercosis
    • Most common parasitic worm infestation of the central nervous system caused by Taenia solium. Easily contracted through contaminated fecal matter or undercooked pork.
  • Toxoplasmosis
    • Parasitic infection passed through contact with cat feces and caused by Toxoplasma gondii.
  • HIV encephalopathy
    • Can lead to progressive subcortical dementia which presents with symptoms misperceived as depression (poor concentration, mood changes, lethargy, social withdrawal)


Neurologic Disorders
  • Parkinson’s disease
    • Depression may be the sole initial presenting symptom and often precedes the development of motor symptoms. Patients with Parkinson’s disease are high risk for suicidal ideations (30% of patients). Make sure to screen for it during their visits.
  • Normal pressure hydrocephalus
  • Stroke
  • Huntington’s disease
  • Post concussion syndrome
    • Occurs in 35-80% of mild traumatic brain injuries and is commonly associated with depression.
  • Multiple sclerosis
    • Depression is very common between 25-50% of patients with a higher rate of suicide attempts.


Endocrine Disorders
  • Hypothyroidism
    • Common symptoms include apathy, psychomotor slowing, depressed mood, and poor memory, which are very similar to depression.
  • Hypoparathyroidism
    • By treating hypoparathyroidism, resolution of depressive symptoms is common.
  • Hypoglycemia
  • Cushing’s syndrome
    • Abnormally high levels of cortisol can lead to depression in 50% of patients; symptoms can be severe enough to trigger suicide.
  • Addison’s disease
    • On the flip side, abnormally low levels of cortisol can also lead to apathy, fatigue, irritable and depression.


Nutritional deficiencies
  • Vitamin B6 deficiency
    • Pyridoxal phosphate, the active form of B6, is a cofactor in the dopamine serotonin pathway. B6 deficiency (which decreases dopamine and serotonin levels) can lead to depression.
  • Folate and Vitamin B12 deficiency


Other disorders
  • Cancers
    • Depression can be associated with brain, pancreas, lung or GI cancer. In pancreatic tumors, a presenting symptom can be depression along with back pain.
  • Systemic lupus erythematosus
    • This chronic autoimmune connective tissue disease is highly associated with neuropsychiatric symptoms (75-90% of patients). It is common to have depression and emotional lability.
  • Anemia
  • Chronic fatigue syndrome
    • It is a common illness with 1 to 4 million Americans suffering from it. It is fairly underdiagnosed by physicians and easily misdiagnosed as depression.
  • Pseudobulbar affect
    • It is an affective disinhibited syndrome often misdiagnosed as depression. It can be secondary to neurodegenerative diseases such as ALS or even head trauma. Patients will present with involuntary, inappropriate outbursts of laughter and/or crying.


Medications and Other Substances
  • Retin-A (topical and oral) medications such as Accutane are commonly used to treat acne. A common side effect is depression. Depression resolves once agent is discontinued.
  • Interferons, used to treat cancer and Hepatitis C, are widely known to cause depression. Patients presenting with depressive symptoms during treatment should be referred to a psychiatrist. Antidepressant treatment can be successful in many cases.
  • Beta-blockers, and other anti-hypertensive agents, can often cause depression. Consider switching to another agent if a patient presents with notable depressive symptoms.
  • Calcium-channel blockers
  • Steroids
  • Statins
  • Alcohol, a central nervous system depressant, when used chronically can cause depression.
  • Benzodiazepines and barbiturates
  • Drugs, especially withdrawal or “crashing” from amphetamine and cocaine, can lead to depressive symptoms.
  • Smoking, on a daily basis, has been shown to cause depression. Quitting smoking for prolonged periods may help decrease these symptoms.


As common as primary depression is, it is crucial to rule out any medical disorders that may be causing secondary depression. Often when these disorders are properly diagnosed and treated, depressive symptoms improve and sometimes even resolve. In addition to obtaining a psychiatric consult, conducting a full physical exam, and drawing basic labs, brainstorm possible medical differentials for patients who present to you with depressive-like symptoms.


Dr. Oh is currently a child and adolescent psychiatry fellow at the University of California in Los Angeles. She completed her adult psychiatry residency at Harbor-UCLA Medical Center in Torrance, CA. She obtained her medical degree from the David Geffen School of Medicine at UCLA. Dr. Oh is interested in reducing stigma against mental health and increasing the awareness and acceptance of treatment especially within the Asian community. Her previous post in this series covered the barriers between psychiatry and internal medicine , medical conditions mimicking psychosis and a work-up of anxiety .


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