No, It Is Not Possible to Be Schizophrenic Yet Neuropsychologically Normal.

Abstract

Cognitive impairment is well documented in schizophrenia, though some reports have been interpreted to suggest that it is possible to have schizophrenia without neuropsychological impairment. The authors tested this by comparing the neuropsychological profiles of closely matched patients with schizophrenia and healthy comparison participants. Sixty-four patients with schizophrenia and 64 healthy comparison cases, matched to within 3 Full-Scale IQ points, were tested using the Wechsler Adult Intelligence Scale (3rd ed.; D. Wechsler, 1997b) and the Wechsler Memory Scale (3rd ed.; D. Wechsler, 1997c). Neuropsychological profiles for these groups were markedly different, with the group of patients with schizophrenia exhibiting performance deficits in memory and speeded visual processing but superior verbal comprehension and perceptual organization relative to the group of healthy comparison participants matched on Full-Scale IQ. Thus, scoring in the normal range does not preclude neuropsychological abnormality in schizophrenia, confirming that neuropsychological impairment is a core feature of the illness.

Applied Short-Form WAIS-III to Explore Global Cognitive Profile of the Patients with Schizophrenia

“…The performance of PIQ is significantly lower than VIQ, and the Processing Speed is the lowest of 4 indexes. The results are consistent with the past findings [9,[14][15][16][17][24][25][26][27].…”

“…Moreover, the mean scores of patients in the Verbal Comprehension and Perceptual Organization indexes were higher than the Working Memory and Processing Speed. Wilk, et al also found that patients with schizophrenia were better than controls on Verbal Comprehension and Perceptual Organization but worse on Working Memory and Processing Speed [24]. Those findings indicated that patients with schizophrenia are impaired in cognitive functions: In the IQ scores, FSIQ was lower than expected, and PIQ was significantly lower than VIQ; in the index scores, the scores from high to low were Verbal Comprehension, Perceptual Organization, Working Memory, and then Processing Speed.…”

Cannabis users have higher premorbid IQ than other patients with first onset psychosis

“…Reading abilities are also widely used in order to infer premorbid IQ in psychosis, as related to measures of full scale IQ, verbal IQ, verbal comprehension (Hanks et al, 2008) and verbal memory (Whitney et al, 2010), the latter being more impaired than general IQ at first episode of psychosis (Mesholam-Gately et al, 2009). This discrepancy between verbal and non-verbal scores in psychotic patients (Wilk et al, 2005) has been shown in people with a genetic liability to develop schizophrenia (Kravariti et al, 2006).…”

Baseline Neurocognitive Deficits in the CATIE Schizophrenia Trial

“…However, they support the notion that briefer test batteries are capable of providing researchers with almost as much information as longer batteries for calculating an overall composite score. As they reduce the time and resources required to conduct an assessment of neurocognition, they may be preferred over longer batteries for the calculation of summary scores in clinical trials (Wilk et al, 2005;Keefe et al, 2004;Velligan et al, 2004). However, brief approaches to the assessment of neurocognition may be more limited in their ability to provide information about specific neurocognitive effects of treatment, which will require more detailed assessment across multiple neurocognitive domains, as recommended in the conclusions of the MATRICS consensus process (Green et al, 2004b).…”