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QCan MS cause a mood disorder such as depression organically—that is, independent of the stress of the disease?
DR. HILLEL PANITCH RESPONDS:
A Depression is very common in MS, though it does not correlate with the degree of disability. However, people with MS are more likely to become depressed than people with ALS, spinal cord injury, or other conditions that have a comparable degree of disability. In addition, depression in MS is more likely to be associated with lesions in the brain than in the spinal cord.
All of this suggests that the depression seen in MS is partly “organic” and not simply caused by the stress of having a disabling disease. Although the exact cause hasn't been determined, it's generally believed that this type of depression is related to the presence of small proteins called cytokines and other substances released by inflammatory cells in relapsing forms of MS, or the loss of neurons that control emotions in progressive forms of MS.
Depression commonly accompanies MS exacerbations but is seldom, if ever, seen as the sole symptom. Sometimes patients report feeling depressed or fatigued, and state that they “feel like they are going to have a relapse,” but other symptoms fail to materialize and the feeling goes away after a few days or weeks. This may or may not be associated with the appearance of new lesions on their MRI scans, and suggests that the depression or fatigue represents a “subclinical” exacerbation—a flare up of MS symptoms of which the patient is unaware aside from these feelings.