A consideration of neuropsychologically normal schizophrenia

Neuropsychological deficits are considered by many to be core features of schizophrenia. However, about 20% of patients with schizophrenia appear to have normal neuropsychological function. This study investigates this subgroup by comparing a "neuropsychologically normal" schizophrenia group to a non-schizophrenic, non-brain damaged patient comparison (PC) sample, and to patients with definitive brain damage who performed normally on neuropsychological testing. All patients completed the Halstead-Reitan Neuropsychological Test Battery and were classified as neuropsychologically normal or impaired using the Average Impairment Rating (AIR). In a sample of 113 patients with schizophrenia, 19.5% were classified as neuropsychologically normal. The brain damaged neuropsychologically normal group (BD-NN) consisted of 14.3% of 124 subjects. These groups were compared with a patient non-schizophrenic, non-brain damaged group who were selected on the basis of having an Average Impairment Rating in the neuropsychologically normal range. The neuropsychologically normal schizophrenic group performed less well than the non-brain damaged, non-schizophrenic patient comparison group on a number of tests, indicating that patients in this group may not be completely neuropsychologically normal, and would be better characterized as "high-functioning" or near normal. The results are discussed in regard to possible neurobiological differences between neuropsychologically impaired and intact schizophrenic patients, and implications for course and outcome.