The genetics of symptom dimensions of schizophrenia: Review and meta-analysis

BackgroundThe use of symptom dimensions of schizophrenia as quantitative phenotypes has been proposed as a mean to reduce the heterogeneity of schizophrenia and facilitate genetic research. However, the genetic background of symptom dimensions is not clear.AimWe aim to investigate whether the symptom dimensions “reality distortion”, “psychomotor poverty” and “disorganization” are heritable phenotypes.MethodWe performed a Medline search including all papers from 1980 to August 2007. In addition to reviewing the articles, we performed meta-analyses on these studies where possible.ResultsWe identified 18 relevant papers. Only the studies on affected sibling pairs were suitable for meta-analysis. Data from twin and affected sibling studies are consistent with a genetic contribution to the disorganization dimension. However these studies did not unequivocally support a large genetic contribution to neither the reality distortion symptom dimension nor to the psychomotor poverty symptom dimension. In contrast several molecular genetic studies did report associations of genes with psychomotor poverty.ConclusionsThese data suggest that only the disorganization symptom dimension may provide an useful alternative phenotype for genetic research. More research is required to make any definitive conclusions.