Cognitive deficits and levels of IQ in adolescent onset schizophrenia and other psychotic disorders

Abstract

Cognitive deficits have been found to be prevalent in early onset schizophrenia. Whether these deficits also characterise other early onset psychotic disorders to a similar degree is unclear, as very few comparative studies have been done. The primary purpose of this study was to compare the profile and severity of cognitive impairments in first-episode early onset psychotic patients who received the schizophrenia diagnosis to those diagnosed with other non-organic, non-affective psychotic disorders. The secondary purpose was to examine whether the profile of cognitive deficits, in terms of intelligence, executive functions, memory, attention and processing speed was global or specific. First-episode psychotic adolescents (N = 39) between the ages 11 and 17 years were included, 18 of whom were diagnosed with schizophrenia, and 21 with other non-organic, non-affective psychoses, using ICD-10 criteria. A healthy control group (N = 40) was included, matched on gender and age. Cognitive functions were assessed using WISC-III/R, the CANTAB battery, WCST, Trail Making B, fluency tasks, and Buschke's selective reminding task. A similar profile and level of impairment was found on measures of attention, executive functions, reaction time, and memory in the schizophrenic and psychotic adolescent groups. However, analyses of WISC-III factor profiles suggested that early onset schizophrenia patients may have more global IQ deficits than non-organic, non-affective psychoses when examined recently after illness onset. Compared to the deficits of adult schizophrenia described in the literature, the results suggest relatively spared simple reaction times in early onset patients.