Schizophrenia is an illness that expresses itself in severe disturbances of thought and behavior. These disturbances include strikingly implausible and bizarre beliefs, suspicions, and interpretations of experience. However, it is not just the contents of thought or what the person with schizophrenia thinks about that is abnormal. The illness also involves deficiencies in thinking with routine and relatively impersonal information and in using this information to solve problems and guide action. Psychiatric pioneers including Kraepelin1 and Bleuler2 recognized this more fundamental cognitive disturbance in schizophrenia at the beginning of the 20th century. Kraepelin suggested that the frontal and temporal lobes of the brain must be affected and characterized the syndrome as a dementia of young people, yet objective evaluation of cognitive brain function has appeared rather recently as a key tool in the study of this complex disorder. Prior to the 1990s, neuropsychological test performance was often regarded as the basis for discriminating schizophrenia from “brain damage.”3 At the same time, there were ideas supported by data that antipsychotic medication might contribute to these deficits.4,5 Moreover, weak or absent relations between psychotic symptoms and scores on standard cognitive tests6,7 seemed to reinforce the idea that impaired cognition was a complication rather than an intrinsic feature of the schizophrenia syndrome.
Heinrichs RW. Cognitive Improvement in Response to Antipsychotic DrugsNeurocognitive Effects of Antipsychotic Medications in Patients With Chronic Schizophrenia in the CATIE Trial. Arch Gen Psychiatry. 2007;64(6):631–632. doi:10.1001/archpsyc.64.6.631