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Why does postpsychotic IQ decline in childhood-onset schizophrenia?
J S Bedwell1, B Keller, A K Smith
1Child Psychiatry Branch, NIMH, Bethesda, MD 20892, USA.
The American Journal of Psychiatry
|December 10, 1999
Summary
Childhood-onset schizophrenia patients show IQ decline not due to dementia, but a reduced ability to learn new skills. This impacts cognitive development during adolescence.
Area of Science:
- Neuroscience
- Developmental Psychology
- Psychiatry
Background:
- Childhood-onset schizophrenia (COS) is associated with significant cognitive deficits.
- The trajectory of intellectual functioning post-psychosis in COS patients remains incompletely understood.
Purpose of the Study:
- To investigate whether the observed decline in full-scale IQ in adolescents with COS is indicative of dementia or a failure to acquire new information and skills.
- To differentiate between neurodegeneration and impaired learning as the cause of cognitive decline.
Main Methods:
- Longitudinal analysis of scaled and raw subtest scores in 31 COS patients using linear regression.
- Correlation of cognitive changes with brain structural changes (hippocampal volume) assessed via magnetic resonance imaging (MRI).
Main Results:
- Significant decline in scaled scores for Picture Arrangement, Information, and Block Design subtests.
- No significant decline observed in non-age-corrected (raw) scores across all subtests.
- A negative correlation was found between reduced hippocampal volume and gains in the Information subtest raw score.
Conclusions:
- The decline in IQ among adolescents with COS does not signify a dementing process.
- The findings suggest an impaired capacity for acquiring new information and skills, rather than neurodegeneration, underlies cognitive decline.
- Hippocampal changes may be linked to difficulties in learning new information.