Screening for Depression in Neurologic Disorders

Depression appears to be particularly common in several neurologic disorders, including epilepsy, stroke, dementias, Parkinson’s disease, Huntington’s disease, and multiple sclerosis. There is some evidence that the ‘‘depression’’ associated with each neurologic disorder is distinct in symptoms and course. This suggests it may be useful to have depression scales validated for each neurologic disorder, yet most instruments appear to yield comparable acceptable sensitivities and specificities. However, head-to-head comparisons of scales and implementation studies are needed to resolve this issue. Depressive disorders are a common psychiatric comorbidity of neurologic disorders, including epilepsy, stroke, dementias, Parkinson’s disease (PD), essential tremor, Huntington’s disease, migraines and multiple sclerosis (MS), to name the principal ones. It is typically assumed that depressive disorders are a complication of these neurologic disorders. However, data published in the past 15 years have suggested a bidirectional relation between depression and stroke, epilepsy, dementia, and PD. In other words, not only are patients with these neurologic conditions at greater risk of developing depression, but patients with depression are at greater risk of developing one of these disorders. Early identification of comorbid depressive disorders is of the essence given their negative impact on quality of life and the course and response to treatment of most of these neurologic disorders. Unfortunately, depression often goes unrecognized and hence untreated. Clearly the use of screening instruments by neurologists may help remedy this problem. Several caveats need to be considered, however. First, the clinical presentation of comorbid depressive disorders may differ in several ways from that of primary depression, such as in cases of depression in epilepsy. Second, several somatic and cognitive symptoms are common in primary depression and most neurologic disorders (ie, fatigue, poor concentration, and slow thinking). Thus, a higher score may be a reflection of such symptoms and not of a depressive episode per se. Third, most of the available screening instruments for depression were developed for primary mood disorders and hence may yield false-positive or -negative findings.