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IQ change in schizophrenia related to brain volume

An imaging study from NeuRA’s Schizophrenia Research Laboratory has confirmed that changes in IQ in people with schizophrenia are related to reduced volume in the brain, and that brain regions are differently affected.

The study was published in JAMA Psychiatry.

Cognitive deficits in schizophrenia, although they can differ from person to person, are one of the core symptoms of the disorder. Earlier work from Associate Professor Tom Weickert’s lab proposed an IQ-based classification system, centred on IQ trajectories from before illness to after illness onset that could identify three distinct subgroups of schizophrenia.

These three subgroups included those who had a large and significant IQ decrease from before to after illness onset (called the deteriorated group); those whose IQ did not appear to change after illness onset staying around or above average before and after illness onset (called the preserved group); and those who displayed consistently low IQ levels before and after illness onset (called the compromised group).

This new research has built on earlier classification work by establishing whether these different intellectual subgroups are associated with any structural changes in the brain. They examined differences in brain volume and were able to confirm that the IQ-based classifications are indeed related to underlying neurobiological differences, and that distinct brain regions may be differentially affected in each subgroup.

The study found that the deteriorated group could be further divided into two subsets – moderately and severely deteriorated subgroups. The severely deteriorated subgroup had significantly reduced brain volume in regions of the brain important for memory, social cognition, language and visual processing, which correspond to more severe negative symptoms (reduced emotions, motivation and social interactions) in the severely deteriorated subgroup in comparison to the preserved group.

“Our recent findings on cognitive IQ-based subgroups provides a strategy to aid in the prediction of how each subgroup would respond to novel therapies to improve cognition and functional abilities in people with schizophrenia,” Assoc Prof Tom Weickert said.