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ABSTRACT & COMMENTARY
Synopsis: This thorough and systemic review of the literature by Carson and colleagues does not support the hypothesis that the risk of depression after stroke is affected by the location of the brain lesion.
Source: Carson AJ, et al. Lancet 2000;356:122-126.
Depression is prevalent in older adults following strokes. More than 20 years ago, researchers reported associations between laterality of experimentally induced brain damage, brain catecholamine concentrations, activity in rats, and later, between left hemisphere strokes and depression in human beings. Since then, the idea that the risk of becoming depressed after a stroke is influenced by the location of the brain lesion has been widely publicized and attractive; however, conflicting evidence has emerged regarding this hypothesis. Some studies have confirmed an association between left hemisphere lesions and depression, while others have not.
Carson and colleagues undertook a systemic review of all reported studies relevant to two questions. The first was that the risk of depression after stroke is higher with left-sided lesions than with right-sided lesions; the second was that the risk of depression is higher with left anterior lesions than with lesions in other sites of the brain. Carson et al conducted meta-analyses of all studies that reported on the association of depression after stroke with the location of the brain lesion. Two investigators systematically reviewed the studies.
A total of 143 studies were identified: 93 studies were excluded because they either did not examine the association between lesion and depression, had unsuitable selection criteria, or presented duplicate data; an additional 13 studies were excluded because they did not include categorical data on depression. A meta-analysis was conducted on the remaining 35 studies.
When all 35 reports were included, lesion location was not associated with depression. Exploration of potential bias sources found no substantial effect of quality, restriction of the analysis to major depressive disorder, the time since stroke at which the assessment of depression was made, or the exclusion of patients with aphasia. To test if the risk of depression is greatest with left anterior brain lesions, studies that differentiated between lesion locations within hemispheres were analyzed. Anterior stroke lesions were the most common, and consequently, carried the greatest absolute risk of depression. However, the relative risk of depression did not differ between the brain regions assessed.
COMMENT BY CLAUDIA A. ORENGO, MD, PhD
This thorough and systemic review of the literature by Carson and colleagues does not support the hypothesis that the risk of depression after stroke is affected by the location of the brain lesion. Left hemisphere lesions, and specifically left anterior lesions, are not associated with an increased risk of depression following stroke. The possibility that a lack of statistical power led to error, hence the negative results, is unlikely because the 95% confidence interval around the main result was narrow. Carson et al performed both fixed-effects and random-effects analyses (which takes into account population heterogeneity) and found similar results.
One previous systemic review of this topic also concluded that no definitive statement about location of stroke and risk of depression could be supported. Therefore, clinicians treating a patient who has had a stroke should not assume that the patient’s risk of depression is related to brain lesion location. (Dr. Orengo is Assistant Professor, Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, Tex.)