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Saturday, March 9, 2013

The Crhr1 Gene, Trauma Exposure, And Alcoholism Risk: A Test Of G × E Effects

The corticotropin-releasing hormone type I receptor (CRHR1) gene has been implicated in the liability for neuropsychiatric disorders, particularly under conditions of stress. Based on the hypothesized effects of CRHR1 variation on stress reactivity, measures of adulthood traumatic stress exposure were analyzed for their interaction with CRHR1 haplotypes and SNPs in predicting the risk for alcoholism.

Phenotypic data on 2,533 non-related Caucasian individuals (1167 alcoholics and 1366 controls) were culled from the publically available Study of Addiction: Genetics and Environment (SAGE) genome-wide association study (GWAS). Genotypes were available for 19 tag SNPs. Logistic regression models examined the interaction between CRHR1 haplotypes / SNPs and adulthood traumatic stress exposure in predicting alcoholism risk.

Two haplotype blocks spanned CRHR1. Haplotype analyses identified one haplotype in the proximal block 1 (p = 0.029) and two haplotypes in the distal block 2 (p = 0.026, 0.042) that showed nominally significant (corrected p < .025) genotype × traumatic stress interactive effects on the likelihood of developing alcoholism. The block 1 haplotype effect was driven by SNPs rs110402 (p = 0.019) and rs242924 (p = 0.019). In block 2, rs17689966 (p = 0.018) showed significant, and rs173365 (p = 0.026) showed nominally significant, gene × environment (G x E) effects on alcoholism status.

This study extends the literature on the interplay between CRHR1 variation and alcoholism, in the context of exposure to traumatic stress. These findings are consistent with the hypothesized role of the extra hypothalamic CRF system dysregulation in the initiation and maintenance of alcoholism. Molecular and experimental studies are needed to more fully understand the mechanisms of risk and protection conferred by genetic variation at the identified loci.

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