IQ subtypes in schizophrenia: distinct symptom and neuropsychological profiles.

Intellectual decline, a key component of cognitive impairment in schizophrenia, varies considerably across individuals. To examine such cognitive heterogeneity, we applied cluster analysis of IQ and oral reading scores in 73 patients with schizophrenia. The following 3 empirically-derived subtypes emerged: intellectually compromised (42%) with similarly subaverage IQ (M = 79.90) and oral reading (M = 84.03); intellectually deteriorated (29%) with subaverage IQ (M = 86.81) but average oral reading (M = 107.71); and intellectually preserved (29%) with average IQ (M = 108.38) and oral reading (M = 104.43). Compromised and deteriorated clusters showed impairments in both executive function and memory, whereas the preserved cluster showed only reduced executive functioning. The 3 clusters also differed in symptom patterns; with intellectually compromised and intellectually deteriorated both rated with higher negative than positive symptoms, in contrast to the opposite pattern of intellectually preserved. Cluster symptom and neuropsychological profiles may help to validate empirically-derived IQ subtypes in schizophrenia.