Does cognitive impairment exist in schizophrenia and bipolar disorder?
Cognitive impairment was once an underappreciated feature of schizophrenia. It was considered an artifact of patients’ symptoms, attention, or motivation problems, but this turned out to be incorrect. Since the 1980s, it has come to be seen as a core feature of the disorder, reliably present in the majority of patients, independent of such positive symptoms as delusions and hallucinations, and a major cause of poor social and vocational outcome (Goldberg et al., 1990;Green, 1996). It is also reliably associated with the neurobiology of the disorder (Goldberg et al., 1995.). It is trait-like and present throughout the course of the illness. Thus, impairment is stable over short (months) and long (years) intervals (Heaton et al., in press). Cognitive impairments in schizophrenia are not epiphenomena. That is, they are not secondary to psychological issues that involve delusions, distracting effects of hallucinations, or gross motivational defects. This has been shown by several approache
