An examination of associations between the inability to taste phenylthiocarbamide (PTC) and clinical characteristics and trait markers in first-episode, nonaffective psychotic disorders

Abstract

Research findings are mixed as to whether or not the inability to taste phenylthiocarbamide (PTC) might represent an endophenotypic trait marker for schizophrenia. We hypothesized associations between PTC-tasting status and select clinical characteristics and trait markers in patients with psychotic disorders that, if present, would provide support for the inability to taste PTC as a trait marker. In a first-episode psychosis sample (n=93), we measured PTC tasting, family history of psychosis, age at onset of prodrome and psychosis, severity of positive and negative symptoms, global impairment in functioning, neurological soft signs, and four neurocognitive domains (verbal learning/memory, visual learning/memory, verbal working memory, and spatial working memory). Associations between PTC-non-tasting and clinical/neurocognitive variables were examined with χ2 tests and independent samples t tests. Among participants, 67.7% tasted PTC in comparison to a strip of control paper, and 25.8% were non-tasters. Tasters and non-tasters did not statistically significantly differ with respect to family history, age at onset, severity of symptoms, neurological soft signs, or the four neurocognitive domains. In conjunction with other findings, it is unlikely that PTC-non-tasting is a trait marker of schizophrenia, though a conclusive study is warranted.

Reasons for Caution When Genotyping Students

“…The ability to taste phenylthiocarbamide (PTC) seems pretty harmless, but there is no clear threshold that separates two clear groups, considerable variation for single people at different times, and the chemical involved is toxic at levels near those used for testing (McDonald, 2011; Campbell et al, 2012). Moreover, there is some evidence that nontasters are at higher risk for schizophrenia (Compton et al, 2013).…”

Anatomical constitution of sense organs as a marker of mental disorders

“…There are several studies that show a correlation between schizophrenia and the alteration of visual perception (such as visual masking, Green et al, 2012 , luminance, size, contrast, orientation and motion perception, Yang et al, 2013 ; Serrano-Pedraza et al, 2014 ), as well as eye movements (Silverstein and Keane, 2011 ). However, vision is not the only sense affected in schizophrenia: aberrant processing of auditory (Micoulaud-Franchi et al, 2014 ), olfactory (Moberg et al, 2014 ), gustative (Compton et al, 2013 ) and tactile (Ferri et al, 2014 ) stimuli also occurs. These are important discoveries for improving our understanding of schizophrenia.…”