The nature and specificity of verbal memory interference in first episode schizophrenia

Chronic schizophrenia patients exhibit attenuated release from proactive interference and increased build-up of retroactive interference compared to healthy individuals. It remains unclear whether abnormal memory interference is present at illness onset. This study investigated the nature and specificity of verbal memory interference in first-episode schizophrenia, and the specific cognitive and clinical correlates of interference. Build-up of PI, release from PI, and build-up of RI data in 72 geographically-represented FE schizophrenia patients recruited from a large catchment area were compared to that of 49 healthy controls and 43 FE bipolar patients matched on age, gender, premorbid IQ, and ethnicity. Results revealed similar verbal memory interference between groups. Although poorer cognitive flexibility and poorer verbal fluency reliably predicted less release from PI in FE patients, this finding was not unique to schizophrenia but rather characteristic of FE psychiatric illness in general. In contrast, poorer executive functioning was unrelated to build-up of RI. Clinical variables of interest (e.g., psychotic symptoms, antipsychotic medication) were largely unrelated to patients’ susceptibility to interference. Importantly, susceptibility to memory interference did not predict eventual delayed verbal recall at illness onset, indicating that it is not a significant contributor to these patients’ memory deficits. Given past findings of attenuated release from PI and heightened build-up of RI in chronic schizophrenia, these results suggest that abnormal memory interference in schizophrenia is not a core feature of the illness (e.g., an endophenotype) but rather develops over time with further illness burden and/or ongoing antipsychotic medications.