Dysthymia and apathy: diagnosis and treatment.

Dysthymia is a depressive mood disorder characterized by chronic and persistent but mild depression. It is often difficult to be distinguished from major depression, specifically in its partially remitted state because "loss of interest" or "apathy" tends to prevail both in dysthymia, and remitted depression. Apathy may also occur in various psychiatric and neurological disorders, including schizophrenia, stroke, Parkinson's disease, progressive supranuclear palsy, Huntington's disease, and dementias such as Alzheimer's disease, vascular dementia, and frontotemporal dementia. It is symptomatologically important that apathy is related to, but different from, major depression from the viewpoint of its causes and treatment. Antidepressants, especially noradrenergic agents, are useful for depression-related apathy. However, selective serotonin reuptake inhibitors (SSRIs) may be less effective for apathy in depressed elderly patients and have even been reported to worsen apathy. Dopaminergic agonists seem to be effective for apathy. Acetylcholine esterase inhibitors, methylphenidate, atypical antipsychotics, nicergoline, and cilostazol are another choice. Medication choice should be determined according to the background and underlying etiology of the targeting disease.