Congenital blindness is protective for schizophrenia and other psychotic illness. A whole-population study.

doi:10.1016/j.schres.2018.06.061

Schizophrenia Research

Volume 202, December 2018, Pages 414-416

https://doi.org/10.1016/j.schres.2018.06.061 Get rights and content

Abstract

Congenital/early blindness is reportedly protective against schizophrenia. Using a whole-population cohort of 467,945 children born in Western Australia between 1980 and 2001, we examined prevalence of schizophrenia and psychotic illness in individuals with congenital/early blindness. Overall, 1870 children developed schizophrenia (0.4%) while 9120 developed a psychotic illness (1.9%). None of the 66 children with cortical blindness developed schizophrenia or psychotic illness. Eight of the 613 children with peripheral blindness developed a psychotic illness other than schizophrenia and fewer had developed schizophrenia. Our results support findings from small case studies that congenital/early cortical but not peripheral blindness is protective against schizophrenia.

Introduction

While visual impairments appear to be a risk factor for schizophrenia (Adams and Nasrallah, 2018; Silverstein and Rosen, 2015; Torrey and Yolken, 2017), since the 1950s it has been observed that congenital and early blindness may be protective (Chevigny and Braverman, 1950). This proposal has been supported by a number of more recent case studies and reviews (Landgraf and Osterheider, 2013; Leivada and Boeckx, 2014; Silverstein et al., 2013). The protection possibly extends to psychotic disorders in general (Leivada, 2016) but not to other mental illness (Silverstein et al., 2013). Two kinds of congenital blindness have been distinguished: peripheral blindness arising in the globe and cortical blindness arising from lesions in the occipital cortex. Critically, it has been suggested that the protective effect is restricted to cortical blindness, not peripheral blindness (Leivada, 2016; Leivada and Boeckx, 2014).

The reliability of this differential protection is important for understanding the aetiology of psychosis. Yet, we are aware of no whole-population studies examining this phenomenon. Our main aim was to use Western Australian State-wide registers to estimate the distribution of cases of schizophrenia among people with congenital and early blindness, examining separately exposure to cortical and peripheral blindness. We hypothesised that congenital and early cortical but not peripheral blindness would be protective against schizophrenia. A secondary aim was to repeat the analyses for the broader diagnostic outcome, psychotic illness.

Section snippets

Methods

This study utilises linkages across administrative health registers, facilitated via the Western Australian Data Linkage System, to build on a broader program of work investigating risk factors for psychotic illness in a cohort of almost 500,000 individuals born in Western Australia between 1980 and 2001. Full details on the cohort and Western Australian whole-population databases and registries have been published (Morgan et al., 2011).

Psychiatric data for the cohort came from hospital

Results

In our cohort of 467,945 children aged between 14 and 35 years at time of psychiatric data extraction, 1870 children had developed schizophrenia (0.4%) while 9120 had developed a psychotic illness including schizophrenia (1.9%).

There were 66 children with cortical blindness (1.4 per 10,000): 60.6% were male and 12.1% were Indigenous; six had at least one parent with a psychotic illness. None of the children with cortical blindness had gone on to develop schizophrenia, nor any other psychotic

Discussion

The results from this whole-population cohort, although possibly underpowered, lend confidence to findings from smaller case studies that congenital or early cortical but not peripheral blindness is protective against schizophrenia. While median lifetime morbid risk for schizophrenia is estimated to be 0.72% (Saha et al., 2005), many of our young cohort had still not passed through the window for schizophrenia onset. Using the age distribution of our cohort, as well as age-of-onset data from

Declaration of interest

The authors have no conflicts of interest to declare in relation to this work.

Author contributions

AJ and VM developed the idea for the study. All authors contributed to the study protocol. MC, JC, GV, DM and VM contributed to data coding and analysis. VM undertook the literature searches and wrote the first draft of the manuscript. All authors contributed to subsequent drafts and have approved the final manuscript.

Acknowledgement

We thank the Data Linkage Branch of the Western Australian Department of Health for data linkage and extraction, and client support. We also thank the custodians of the Western Australian Hospital Morbidity and Mental Health Data Collections, the Western Australian Midwives Notification System, and the Western Australian Register of Developmental Anomalies for the provision of data.

This study was approved by the Western Australian Department of Health Human Research Ethics Committee (2011/75)

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Letter to the EditorCongenital blindness is protective for schizophrenia and other psychotic illness. A whole-population study.

Abstract

Introduction

Section snippets

Methods

Results

Discussion

Declaration of interest

Author contributions

Acknowledgement

Schizophr. Res.

Neurosci. Lett.

Schizophr. Res. Cogn.

The Adjustment of the Blind

“To see or not to see: that is the question.” The “Protection-Against-Schizophrenia” (PaSZ) model: evidence from congenital blindness and visuo-cognitive aberrations

Front. Psychol.

Letter to the Editor
Congenital blindness is protective for schizophrenia and other psychotic illness. A whole-population study.