Summary: A recent review of genetic and population studies reveals that premorbid cognitive deficits in schizophrenia, such as lower IQ, are largely due to neurodevelopmental disruptions rather than inherited genetic variants that directly increase schizophrenia risk.
The findings suggest that non-familial factors, including rare genetic mutations and environmental influences, play a significant role in both cognitive impairments and schizophrenia risk. This challenges the long-held belief that cognitive deficits and schizophrenia share the same genetic origins.
The research highlights the need to explore early neurodevelopmental disruptions to develop prevention and treatment strategies for both cognitive impairment and schizophrenia.
Key Facts:
- Premorbid cognitive deficits in schizophrenia stem from neurodevelopmental disruptions, not inherited genetics.
- Non-familial factors, including rare genetic mutations, are key contributors.
- Understanding neurodevelopmental disruptions could lead to better prevention strategies.
Source: Genomic Press
In a comprehensive review of recent genetic and population studies, published in the peer-reviewed medical journal Genomic Psychiatry (Genomic Press, New York), Professors Michael Owen and Michael O’Donovan of Cardiff University’s Centre for Neuropsychiatric Genetics and Genomics present evidence that challenges conventional wisdom about cognitive deficits in schizophrenia.
Their analysis reveals that premorbid cognitive impairment – lower IQ and other cognitive deficits present before the onset of psychosis – is largely explained by non-familial factors rather than by the same inherited genetic variants that increase risk for schizophrenia itself.
“For decades, we’ve assumed that premorbid cognitive problems in people with schizophrenia were directly caused by the same genetic factors that cause the disorder,” said Professor Owen.
“Our review of the latest research suggests this isn’t the case. Instead, it appears that neurodevelopmental disruptions are responsible for both the cognitive deficits and the increased risk of developing schizophrenia.”
Key findings from the review include:
- Premorbid cognitive impairment marks the presence of an underlying disruption of neurodevelopment that increases risk for schizophrenia, but cognitive impairment is not in itself causal for schizophrenia.
- The degree to which an individual’s cognitive ability deviates from what would be expected based on family history is a better predictor of the underlying neurodevelopmental disturbance that increases schizophrenia risk than is absolute cognitive ability.
- The neurodevelopmental disturbance does not appear to be primarily caused by the same familial factors, including inherited common genetic variants, that increase schizophrenia risk or that typically influence cognitive ability in the general population. Instead, rare genetic variants including copy number variations (CNVs) and damaging coding mutations that occur as new or de novo mutations contribute, as do other non-familial environmental risk factors.
- There is evidence for further cognitive decline after diagnosis in some individuals, as well as an increased risk of dementia, but this does not appear to be substantially related to genetic risk for neurodegenerative disorders.
The researchers propose a model in which neurodevelopmental perturbations, largely influenced by non-familial factors, lead to both cognitive impairment and increased vulnerability to schizophrenia.
They also challenge the idea of a distinct “neurodevelopmental subtype” of schizophrenia, instead suggesting a spectrum of neurodevelopmental impairment across the disorder.
“These findings have important implications for how we think about schizophrenia and cognitive impairment,” said Professor O’Donovan.
“Understanding the causes of early neurodevelopmental disruptions will be important for developing interventions aimed at preventing or mitigating both the cognitive deficits and schizophrenia risk.”
The research also highlights the need for further investigation into the causes of cognitive decline after schizophrenia onset, as well as the increased risk of dementia in this population. Understanding these processes could lead to new approaches for preserving cognitive function in individuals with schizophrenia throughout their lives.
This review represents a significant advance in our understanding of the complex interplay between genetics, cognition, and schizophrenia risk.
It paves the way for more targeted research into the underlying mechanisms of cognitive impairment in schizophrenia and may ultimately inform the development of new prevention and treatment strategies.
About this schizophrenia and cognition research news
Author: Ma-Li Wong
Source: Genomic Press
Contact: Ma-Li Wong – Genomic Press
Image: The image is credited to Neuroscience News
Original Research: Open access.
“The genetics of cognition in schizophrenia” by Michael Owen et al. Genomic Psychiatry
