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Intellectual functioning in first-episode schizophrenia, schizoaffective disorder and bipolar disorder

University of British Columbia

Intellectual functioning (IQ) prior to the onset of illness (premorbid IQ) and the pattern of its trajectory across illness onset can inform us of the early developmental pathology of mental disorders. The goals of this study were to 1) investigate these features in first-episode psychiatric patients with overlapping symptoms including schizophrenia (SZ), schizoaffective disorder (SA) and bipolar disorder (BD), as well as to 2) examine these features and the presence of psychosis, and the influence of mood-incongruent features, in BD patients. To address these objectives, SZ, SA, BD-I, and healthy controls, aged 17-37 years, were pooled from two early-intervention programs. The North American Adult Reading Test was used to estimate premorbid IQ, while the Kaufman Brief Intelligence Test was used to measure current IQ. Group differences in premorbid IQ and IQ trajectories were evaluated with ANOVA and repeated measure ANOVA. Both controls and BD patients had significantly higher premorbid IQ compared to SZ patients, BD patients had scores comparable to control, and there was a strong trend of premorbid IQ deficit in SA patients. Regarding IQ change, only subjects with SA and SZ experienced significant IQ deterioration through illness onset. Regarding psychosis, t-tests deciphered a strong, although insignificant, premorbid IQ difference across BD patients, with deficits seen in psychotic but not non-psychotic patients. Lastly, t-tests revealed a significant decline in IQ across psychotic BD patients with mood-congruent, and not –incongruent, features. Secondary post-hoc analyses revealed that this finding might be attributable to the type of antipsychotic that patients received. Taken together, these results suggest that early neurodevelopmental pathology, which most likely directly affects intellectual functioning, may be different in BD than in SA and SZ. Furthermore, low premorbid IQ could be a potential risk factor for psychosis. Assessment of IQ before and after illness onset could help facilitate early identification of psychopathology and assist with patient management and care.

Text

2015-01-07

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/51790

Neuroscience

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/