Background: Twin and adoption studies have consistently implicated genes in the etiology of schizophrenia. Molecular genetic studies have found some consistent support for linkage to many regions of the genome. Despite these encouraging results, none of these findings have achieved genome-wide levels of statistical significance, and none have been consistently replicated.
Methods: This report is a follow-up of a genome scan that analyzed linkage to the diagnosis of schizophrenia in a series of sibling pairs in the National Institute of Mental Health Genetics Initiative for Schizophrenia data. In this report, we use the same sample to assess linkage to three quantitative traits developed from the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms: positive, negative, and disorganized symptoms.
Results: We show suggestive linkage to chromosomes 6, 9, and 20 for the disorganized trait and to chromosome 12 for the negative trait. We also show weak association with PAH (phenylalanine hydroxylase) on that chromosome.
Conclusions: The findings on chromosome 6 replicate some prior findings, the other loci are novel. A larger sample would provide more power to detect both linkage and association for this complex disorder.