Depression in multiple sclerosis: Relationship to planning ability

Recent research has demonstrated deficits on effortful executive tasks invo lving planning in multiple sclerosis (MS) patients. Given the high prevalen ce of depression in MS and the commonly reported link between depression an d performance on executive tasks, planning impairments in MS may be associa ted with depression. We compared the performance of depressed and nondepres sed MS patients on a planning task (Tower of London-TOL) to evaluate this h ypothesis. Compared with nondepressed MS patients, depressed MS patients ma de significantly (p < .05) more moves and took more time per trial on the T OL. A follow-up regression analysis was conducted that included the TOL and speeded attentional/working memory task indices found to be associated wit h depression in MS from the authors' prior reports. This analysis revealed that 25% of the variance in depression scores was predicted by the most sen sitive speeded attentional/working memory task. Furthermore, this variance overlapped completely with variance predicted by the TOL-time/trial index. The only clearly nonspeeded task index, TOL-moves per trial, was associated with unique variance (8%) in predicting MS depression scores. These result s suggest that slowed information processing speed and, secondarily, defici ent nonspeeded central executive skill, may be core to the cognitive defici ts characteristic of depressed MS patients.