Depression in multiple sclerosis: Relationship to working memory capacity

Recent research has shown that depression in multiple sclerosis (MS) is ass ociated with deficits on cognitively demanding tasks. One explanation for t his relationship is that depressed MS patients may have reduced working mem ory capacity. The present study was designed to test this hypothesis. Depre ssed MS patients were compared with nondepressed MS patients and nondepress ed healthy controls on a task of working memory capacity (reading span) and a short-term memory task not taxing working memory capacity (word span). I n support of the capacity-reduction model, compared with the nondepressed g roups, depressed MS patients performed significantly worse on reading span (p < .001) but not on word span. Additionally, reading span was significant ly correlated with capacity-demanding tasks shown to be impaired in depress ed MS patients in previous reports. Results suggest that depressed MS patie nts are characterized by limited working memory capacity and that the centr al executive component of the working memory system may be most affected.