Summary: The retina, as part of the central nervous system, may reflect early signs of brain disorders like schizophrenia. A large-scale genetic study found that people with higher genetic risk for schizophrenia tend to have thinner retinas, even in the absence of symptoms.
These subtle changes were detected using optical coherence tomography, a fast and non-invasive eye scan. The findings also support the inflammation hypothesis of schizophrenia, suggesting new possibilities for early detection and treatment.
Key Facts:
- Retinal Link: Higher genetic risk for schizophrenia is associated with thinner retinas.
- Non-Invasive Detection: Retinal thickness can be measured in minutes using optical coherence tomography.
- Inflammation Connection: Genetic variants tied to inflammation may underlie both brain and retinal changes in schizophrenia.
Source: University of Zurich
The retina is part of the central nervous system and therefore a direct extension of the brain. This is why changes in the brain could potentially also be detected in our eyes.
An international team of researchers led by the University of Zurich and the University Hospital of Psychiatry Zurich has now tackled this very question.
In their study, the researchers examined whether changes in our nerve connections are linked to a genetic risk for schizophrenia, as impaired neural information processing is one of the main characteristics of the disorder.
Previous studies suggest that schizophrenia not only reduces volume of gray matter in the brains of those affected, but that it also leads to loss of retinal tissue. However, whether these changes are the cause of schizophrenia or a consequence of the disorder has remained unanswered.
Retinal health could also be affected by schizophrenia itself, for example through antipsychotic medication, lifestyle factors or diabetes.
Extensive use of data from healthy individuals
“To investigate whether the risk of developing schizophrenia has an effect on the central nervous system, we examined tens of thousands of healthy individuals,” says Finn Rabe, first author of the study and postdoc at the University of Zurich.
“We then calculated polygenic risk scores for each individual.”
The researchers were able to use extensive genetic and retinal data taken from the UK Biobank, a large biomedical database containing data from over half a million people.
“You could say that the scale of the UK Biobank’s data has revolutionized biomedical research,” the researcher adds.
Thin retina, elevated risk
The study shows that higher genetic susceptibility to schizophrenia is indeed associated with thinner retinas. However, the effects are small and can only be reliably demonstrated in large-scale studies.
One of the study’s findings is that, unlike changes in the brain, changes in the retina are easy to detect using non-invasive and inexpensive retinal measurements.
Thanks to optical coherence tomography, which can be described as a kind of ultrasound for the eye, retinal thickness can be measured within a matter of minutes.
This offers a promising outlook for prevention. “Our study shows the potential of using optical coherence tomography in clinical practice. But large-scale longitudinal studies are needed to examine how useful it will be for prevention,” says Finn Rabe.
Perspectives for new therapies
Another key finding of the study concerns genetic variants associated with inflammatory processes in the brain. These may also contribute to structural changes in the retina.
The study thus offers further support for the inflammation hypothesis of schizophrenia, i.e., the idea that inflammatory processes contribute to the development or progression of the disorder.
“If this hypothesis is confirmed, inflammation could be interrupted by medication, potentially enabling us to improve treatment possibilities in the future,” says Rabe.
About this visual neuroscience and schizophrenia research news
Author: Melanie Nyfeler
Source: University of Zurich
Contact: Melanie Nyfeler – University of Zurich
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Genetic susceptibility to schizophrenia through neuroinflammatory pathways associated with retinal thinness” by Finn Rabe et al. Nature Mental Health
Abstract
Genetic susceptibility to schizophrenia through neuroinflammatory pathways associated with retinal thinness
Schizophrenia is associated with structural and functional changes in the central nervous system, including the most distal part of it, the retina.
However, the question of whether retinal atrophy is present before individuals develop schizophrenia or is a secondary consequence of the disorder remains unanswered.
Here we address this question by examining the association between polygenic risk scores for schizophrenia and retinal morphologies in individuals without a schizophrenia diagnosis.
We used population data for 34,939 white British and Irish individuals from the UK Biobank.
Our robust regression results show that higher polygenic risk scores for schizophrenia were associated with thinner overall maculae, while controlling for confounding factors (b = −0.17, P = 0.018).
Similarly, we found that greater polygenic risk scores for schizophrenia specific to neuroinflammation gene sets were associated with thinner ganglion cell inner plexiform layers (b = −0.10, self-contained P = 0.014, competitive P = 0.02).
These results provide new evidence for genetic factors that could predispose individuals to heightened neuroinflammatory responses.
Over time, these responses could contribute to neurodegenerative processes such as retinal thinning.
