Neurocognition
Neurocognition is commonly impaired in patients with schizophrenia in all stages of the illness and varying levels of severity. While these impairments may appear prior to the onset of psychosis, their severity in chronic schizophrenia patients is about 1.5 to 2.0 standard deviations below the healthy population. Neurocognitive impairment is a central clinical feature of schizophrenia, as it is associated with pre-morbid history, concurrent brain functioning, and functional outcomes, and is under consideration as a possible component of the diagnosis for schizophrenia in DSM-V and ICD-11. Despite the centrality of cognition in schizophrenia, there are no proven pharmacologic treatments currently available. Spurred by the NIMH Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) initiative, a pathway for FDA approval of compounds to improve cognition is being established including an approved battery of tests, the MATRICS Consensus Cognitive Battery (MCCB), and numerous clinical trials are underway to identify new treatments. While these studies utilize newly established methods primarily developed to assess cognition in stable patients with schizophrenia, the methods for assessing cognition in patients who require a change in antipsychotic may differ. Most published studies of cognition have used samples of convenience that have included groups of patients who can complete extensive research protocols due to their chronic institutionalization or who are available because they have entered a clinical trial or other specialized research study, and have thus been carefully screened with extensive exclusion criteria, such as the absence of substance abuse and medical co-morbidities.
