Defining a cognitive function decrement in schizophrenia

Should cognitive impairment be included in the diagnostic criteria for schizophrenia?

“…In healthy controls, current cognitive ability is clearly predicted by antecedent factors such as maternal education and reading score (30). The healthy controls whose mothers had greater education had higher cognitive functions.…”

“…Thus, the evaluation of a patient's cognitive impairment must place the cognitive data in the context of his or her background and educational history (26). On the other end of the spectrum, some patients who had demonstrated high levels of cognitive skills early in their lives may have cognitive performance that is in the "normal range" despite significant decline from high premorbid levels (30). How will diagnosticians determine how historical and demographic factors interact with a patient's illness to result in his or her current cognitive levels?…”

Virtual faces as a tool to study emotion recognition deficits in schizophrenia

“…Regarding the level of own education it is well-known that that individuals with schizophrenia do not perform on cognitive tests at the level predicted by their parental education. While schizophrenia patients may score within the normal range on cognitive tests, it is likely that these patients have suffered a decrement in their cognitive functions (Keefe et al, 2005). These findings have led to the assertion that matching schizophrenic patients and normal control subjects on education or IQ may cause systematic mismatching of theoretically expected ability (the 'matching fallacy'; Meehl, 1970) as the educational failure and reduced IQ seem to be related to the illness itself.…”

“…Because schizophrenia patients may have suffered a decrement in their cognitive functions that is related to the illness itself (Keefe et al, 2005) we additionally matched patients and control subjects according to years of parental education (± 2 years) rather then according to own educational attainment. There were no significant differences between groups on these demographic variables (see Table 1).…”

Baseline Neurocognitive Deficits in the CATIE Schizophrenia Trial

“…Neurocognition is moderately to severely impaired in patients with schizophrenia (Heinrichs and Zakzanis, 1998), and almost all patients demonstrate some measure of decline from their expected level of neurocognitive function (Keefe et al, 2005). Neurocognitive impairment is a core feature of schizophrenia, and not simply the result of the symptoms or the current treatments of the illness (Green et al, 2004b).…”