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Ask the Experts

Question:

Given that most states of depression are not due to an underlying infection, could you tell us what clues tip you off that infection may be the cause in specific patients?

Answered by: Brian Fallon

In our training as doctors, we learn that the patient's history will tell us most of what we need to know.

If a person develops depression completely out of the blue without recent stressors or a family history suggestive of a congenital predisposition, then one has to consider that there may be an underlying infectiousmedical cause.

The list for the medical differential diagnosis of depression is long, but would include exploration of neurological (e.g., multiple sclerosis), multisystemic (e.g, systemic lupus), infectious (e.g., Lyme disease, HIV), endocrine (e.g., thyroid), hematologic (vitamin B12 deficiency, anemia), malignant (e.g., pancreatic cancer), traumatic (e.g., subdural hematoma), and cardiovascular (e.g., reduced cardiac output) causes.

If a person reports a recent history of flu-like symptoms, such as unrelenting fatigue, coughing, sore throat, fever, enlarged lymph nodes, or diarrhea, then this would increase the likelihood of an infectious cause.

If a person has symptoms that would be atypical for depression alone (e.g. arthralgias or radicular pains), multisystemic medical etiologies need to be considered.

Further, if a person's depression is not responding to the treatments that commonly are effective, one should re-examine the possibility of an undetected medical illness. In our part of the country, where Lyme disease is so endemic, symptoms such as arthralgias, myalgias, unusual rashes, tick bite, shooting pains, numbness and tingling, cognitive problems, intense headaches, and/or severe fatigue would all be signs suggestive of the diagnosis of Lyme disease. While laboratory tests are helpful, the clinical history most often points to the cause.