Understanding processing speedits subcomponents and their relationship to characteristics of people with schizophrenia

Introduction Processing speed has been advanced as one of the core cognitive deficits of schizophrenia. Several methods were developed to assess this domain; however, most tasks, despite indexing several cognitive and motor components, tend to characterise processing speed as a unitary construct. This study explores potential subcomponents of processing speed in schizophrenia and their relationship with demographic, clinical, and neuropsychological characteristics. Methods One hundred and sixty participants with a diagnosis of schizophrenia were assessed on neuropsychological tasks measuring processing speed, executive function, and memory. Demographics and clinical characteristics were also recorded. Three independent measures were extracted to account for subcomponents of processing speed: behavioural execution, response processing, and accuracy. Results The identified components of processing speed were differently predicted by demographic characteristics, clinical characteristics, and overall intelligence estimates. Age and symptom severity were important predictors for behavioural execution; intelligence and social withdrawal predicted response processing; and accuracy was predicted by illness duration. Correlations showed executive function and memory to be associated with response processing and accuracy but not with behavioural execution. Conclusions Distinct characteristics of schizophrenia seem to predict processing speed subcomponents. Distinguishing between behavioural, processing, and accuracy may be a useful way forward to refine our understanding of processing speed impairment in schizophrenia.