CHRNA5 and schizophrenia: A recent genome-wide association study of schizophrenia (Schizophrenia-Working-Group-of-the-Psychiatric-Genomics-Consortium, 2014) identified a locus in the CHRNA5-A3-B4 gene cluster on chromosome 15, which has been consistently shown to be associated with heaviness of smoking (Tobacco-and-Genetics-Consortium, 2010).