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

Abstract

The causes of schizophrenia are still unknown. For the last 100 years, though, both “absent” and “perfect” vision have been associated with a lower risk for schizophrenia. Hence, vision itself and aberrations in visual functioning may be fundamental to the development and etiological explanations of the disorder. In this paper, we present the “Protection-Against-Schizophrenia” (PaSZ) model, which grades the risk for developing schizophrenia as a function of an individual's visual capacity. We review two vision perspectives: (1) “Absent” vision or how congenital blindness contributes to PaSZ and (2) “perfect” vision or how aberrations in visual functioning are associated with psychosis. First, we illustrate that, although congenitally blind and sighted individuals acquire similar world representations, blind individuals compensate for behavioral shortcomings through neurofunctional and multisensory reorganization. These reorganizations may indicate etiological explanations for their PaSZ. Second, we demonstrate that visuo-cognitive impairments are fundamental for the development of schizophrenia. Deteriorated visual information acquisition and processing contribute to higher-order cognitive dysfunctions and subsequently to schizophrenic symptoms. Finally, we provide different specific therapeutic recommendations for individuals who suffer from visual impairments (who never developed “normal” vision) and individuals who suffer from visual deterioration (who previously had “normal” visual skills). Rather than categorizing individuals as “normal” and “mentally disordered,” the PaSZ model uses a continuous scale to represent psychiatrically relevant human behavior. This not only provides a scientific basis for more fine-grained diagnostic assessments, earlier detection, and more appropriate therapeutic assignments, but it also outlines a trajectory for unraveling the causes of abnormal psychotic human self- and world-perception.

Seasonality of births in horizontal strabismus: comparison with birth seasonality in schizophrenia and other disease conditions

“…The nature of the association between exotropia and schizophrenia remains unclear, but vision appears to be fundamental for the development of schizophrenia. Congenital blindness (or very early loss of vision) has been reported to protect against developing schizophrenia, 64,65 while abnormal vision and/or abnormal early visual experiences (as would be frequent in children with exotropia) appears to be a significant risk factor for schizophrenia. 13 Our findings raise the possibility that exotropia is a risk factor specifically for deficit schizophrenia.…”

Schizophrenia and cortical blindness: protective effects and implications for language

“…The PaSZ hypothesis distinguishes between two factors as well: (a) age of blindness onset and (b) degree of visual capacity (i.e., blindness, impairment, normal vision, highly trained vision, etc.). The second factor is indeed relevant in the context of Landgraf and Osterheider ( 2013 ), where the relative risk for schizophrenia is related to a continuum of visual capacity toward a “peak risk” (see also Landgraf et al, 2012 ; Silverstein et al, 2013a ). Both sets of factors enter into the relation between schizophrenia and blindness, but in the context of the present discussion the second factor of the PaSZ hypothesis is not so crucial, because we focus on the one edge of the continuum (i.e., blindness).…”

“…The absence of reports of schizophrenic patients with CB has been repeatedly noted, and has led to the claim that CB confers a protective effect against schizophrenia (Chevigny and Braverman, 1950 ; Horrobin, 1979 ; Riscalla, 1980 ; Sanders et al, 2003 ; Silverstein et al, 2013a ; Postmes et al, 2014 ). We will refer to this as the “Protection-Against-Schizophrenia” (PaSZ) hypothesis (Landgraf and Osterheider, 2013 ). This hypothesis predicts a decreased risk for developing schizophrenia in the blind population (for a schematic representation, see Landgraf and Osterheider, 2013 : Figure 1).…”

“…We will refer to this as the “Protection-Against-Schizophrenia” (PaSZ) hypothesis (Landgraf and Osterheider, 2013 ). This hypothesis predicts a decreased risk for developing schizophrenia in the blind population (for a schematic representation, see Landgraf and Osterheider, 2013 : Figure 1).…”

“…Although the protective effects of CB have been recently documented (see Landgraf and Osterheider, 2013 ; Silverstein et al, 2013a on possible cognitive changes as well as neurofunctional and multisensory reorganization effects), certain issues remain to be clarified. It is the aim of this paper to do so.…”