Background. We wished to assess the effect of three types of medication on verbal memory impairments in schizophrenia.
Method. Forty-eight patients with schizophrenia and 40 healthy control subjects underwent a battery of verbal memory tasks, including free recall, recognition and short-term memory span. All the patients were on antipsychotic medication. In addition, 24 were taking anticholinergic drugs (benztropine) and 30 were taking benzodiazepines. A subsample of 39 had clinical ratings for depressive symptoms. Regression analyses were conducted on the memory measures in this subsample, with negative symptoms, depression, type of antipsychotic medication (conventional v. atypical), benzodiazepines and anticholinergic drugs as predictors.
Results. Type of antipsychotic medication made no significant contribution to memory deficits and benzodiazepine use made very little contribution. However, anticholinergic medication was a predictor of memory impairment, especially with regard to semantic organization. Complementary analyses revealed that patients taking any type of drug with anticholinergic activity (benztropine and/or antipsychotic agents) were significantly impaired relative to the other patients on measures reflecting free recall efficiency and semantic organization.
Conclusions. Drugs with anticholinergic activity are the major pharmacological agents that contribute to the verbal memory deficit observed in patients with schizophrenia. These drugs appear to act by impeding semantic organization at encoding.