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Dopaminergic foundations of schizotypy as measured by the German version of the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE)—A suitable endophenotype of schizophrenia

Personality Psychology and Individual Differences, Department of Psychology, Justus-Liebig-University Giessen Giessen, Germany.
Frontiers in Human Neuroscience (Impact Factor: 2.9). 01/2013; 7:1. DOI: 10.3389/fnhum.2013.00001
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ABSTRACT The concept of schizotypy or "psychosis proneness" captures individual differences in perceptual, cognitive, and affective experiences that may relate to a range of psychotic disorders. The concept is an important way to assess the contribution of pre-existing psychological and genetically based biological features to the development of illnesses such as schizophrenia (so called endophenotypes). The Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE) is a widely used multi-dimensional measure of the construct and consists of four scales which mirror several groups of psychotic symptoms: Unusual Experiences (UnEx; positive symptoms), Cognitive Disorganization (CogDis; cognitive symptoms), Introvertive Anhedonia (IntAn; negative symptoms), and Impulsive Nonconformity (ImpNon; impulsive and antisocial symptoms). For the purpose of evaluating the suitability of schizotypy as an endophenotype of schizophrenia the current version of the O-LIFE was translated into German: its psychometric properties (including re-test reliability and construct validity) were examined in a large sample (n > 1200) and compared to those of the English original. The German version was both highly reliable and consistent with the original. The study aimed to show that schizotypy as measured by the O-LIFE can indeed be regarded as an endophenotype of schizophrenia in terms of genetic associations regarding relevant dopamine-related candidate polymorphisms of schizotypy [i.e., Val(158)Met-polymorphism of the COMT gene, uVNTR of the MAOA gene, Taq1A-polymorphism of the DRD2 gene, VNTR of the SLC6A3 (DAT) gene]. We also wanted to compare the genetic associations of the O-LIFE to those published using other operationalizations of schizotypy. Our results show a large number of significant associations and borderline-significant trends between the O-LIFE sub-scales and a range of genes, thereby supporting using the O-LIFE in the search for endophenotypic markers.

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    • "patients present with a later age of onset of psychotic illness and fewer negative symptoms (Murphy et al., 1999). A growing body of evidence suggests that schizotypy is an endophenotype for schizophrenia (Siever et al., 1990; Kendler et al., 1993; Bergman et al., 1996; Cadenhead et al., 2000; Vollema and Hoijtink, 2000; Fanous et al., 2007; Grant et al., 2013). An excess of schizotypal traits has also been reported in people with 22q11.2DS "
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