IQ Trajectory, Cognitive Reserve, and Clinical Outcome Following a First Episode of Psychosis: A 3-Year Longitudinal Study

Abstract

Comparison of current and estimated premorbid IQ in schizophrenia suggests that there are subgroups with low IQ, deteriorated IQ (DIQ), or preserved IQ and that this is established by psychosis onset. There are no controlled studies examining the trajectory of these IQ subgroups longitudinally or their relationship with clinical and social outcomes. Of 129 individuals with first-episode schizophrenia or schizoaffective disorder, 25% showed stable low IQ, 31% showed stable IQ in the average/high range, and 44% demonstrated intellectual deterioration by 10 points or more. Patients in the low and deteriorated groups were equally impaired on tests of memory and executive function compared with the preserved average/high-IQ group and controls and showed more negative and disorganization symptoms than the preserved average/high-IQ group. Sixty patients and 27 controls were assessed again 1 and 3 years later. There was no evidence that those with IQ deterioration at baseline continued on a declining cognitive trajectory or that those with preserved average/high IQ experienced subsequent IQ decline. The low IQ group showed no change in IQ, whereas both the DIQ and the preserved IQ groups improved. However, the rate of improvement of these 2 subgroups was no greater than that of the healthy controls, suggesting that this reflected practice effects. Both the low and the deteriorated groups had longer index admissions, more core negative symptoms, and worse occupational outcomes at 3 years. These data suggest that following psychosis onset, IQ is stable and that it is IQ at psychosis onset rather than premorbid IQ predicts a more severe illness.

Intellectual Functioning of Individuals with Mental Disorders on Wechsler Adult Intelligence Scale –Revised (WAIS –R)

“…Amminger et al (2002) further suggested that untreated psychoses compromise some aspects of cognitive functions. Later Joyce et al (2005) revealed that half of people with schizophrenia in this study had preserved IQ in normal range after the onset of disorder but there was evidence of a specific impairment in special working memory even in those with high/average IQ; (40%) had generalized cognitive decline, similar results were also revealed by Lesson, et al (2009).…”

“…It has been observed during our clinical experience that clients with depression and anxiety disorders often have reality contact and their social, occupation and daily functioning is much better then people with schizophrenia because it is more severely disturbed mental disorder. Lesson, et al (2009) also showed that IQ at psychosis onset rather than premorbit IQ predicts a more severe illness.…”

Preserved, deteriorated, and premorbidly impaired patterns of intellectual ability in schizophrenia.

“…In light of the heterogeneity in intellectual performance patterns observed in schizophrenia and given the inconsistencies in the literature regarding issues of intellectual decline, premorbid impairments, and preserved abilities, a typology comprising preserved, deteriorated, and premorbidly impaired intellectual ability patterns has been proposed and received partial support (Badcock, Dragović, Waters, & Jablensky, 2005;Leeson et al, 2011).…”

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

“…We calculated a difference score (IQ minus premorbid IQ) in order to see whether the estimated deterioration was associated with cannabis use (see also Leeson et al, 2011), and found this to be the case. This raises the possibility of a neuroprotective action of cannabis.…”