Muglia and colleagues (2008) reported that the protein tyrosine phosphatase receptor PTPRN was significantly associated with major depression: in the current report, two other protein tyrosine phosphatase receptors, PTPRD and PTPRS, are significantly associated with the comorbid phenotype. In addition, nine genes identified in the current study have been associated with smoking cessation success (Uhl et al., 2008): CDH13, CTNNA2, CLSTN2, SEMA5A, PTPRD, CREB5, SOX5, GRIN2A, and CCBE1. Perhaps these genes are generally associated with addiction-related traits. These results are summarized in Table 3, which also includes the results of a systematic search of the NCBI Gene database and the NCBI Association Results browser of genes harboring a marker with p<10−3 to determine whether it has been previously associated with phenotypes related to substance use problems or internalizing symptoms.
