AUTHOR=Grant Phillip , Kuepper Yvonne , Mueller Eva , Wielpuetz Catrin , Mason Oliver , Hennig Juergen 

TITLE=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

JOURNAL=Frontiers in Human Neuroscience

VOLUME=7

YEAR=2013

URL=https://www.frontiersin.org/journals/human-neuroscience/articles/10.3389/fnhum.2013.00001

DOI=10.3389/fnhum.2013.00001

ISSN=1662-5161

ABSTRACT=<p>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 (<italic>n</italic> &gt; 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<sup>158</sup>Met-polymorphism of the <italic>COMT</italic> gene, uVNTR of the <italic>MAOA</italic> gene, Taq1A-polymorphism of the <italic>DRD2</italic> gene, VNTR of the <italic>SLC6A3</italic> (<italic>DAT</italic>) 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.</p>