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Monday, December 5, 2011

Prediction of the Risk of Comorbid Alcoholism in Schizophrenia by Interaction of Common Genetic Variants in the Corticotropin-Releasing Factor System

Stress plays a major role in the development of comorbid alcohol use disorder (AUD). In turn, AUD worsens the outcome of psychiatric patients with respect to global disease severity, social situation, and socioeconomic burden. Prediction of persons at risk for AUD is crucial for future preventive and therapeutic strategies.

To investigate whether genetic variants of the corticotropin-releasing factor system or their interaction influence the risk of developing AUD in chronic disease populations.

Genotype analysis comprising selected single-nucleotide polymorphisms within the CRHR1 and CRHBP genes in patients with schizophrenia and in a nonschizophrenic psychiatric disease control sample should allow the extraction of predictors of comorbid AUD. Gene expression (messenger RNA) analysis in peripheral blood mononuclear cells was performed to gain the first mechanistic insight.

An ideal setup for this study was the Göttingen Research Association for Schizophrenia Data Collection of schizophrenic patients, specifically intended to enable association of genetic information with quantifiable phenotypes in a phenotype-based genetic association study.

Patients A total of 1037 schizophrenic patients (Göttingen Research Association for Schizophrenia sample), 80 nonschizophrenic psychiatric disease controls as a small replicate sample, and a case-control study including 1141 healthy subjects.

Main Outcome Measures Association of CRHR1 and CRHBP genotypes with the following: (1) AUD; (2) a newly developed alcoholism severity score comprising 5 AUD-relevant variables; and (3) quantitative CRHR1 and CRHBP messenger .RNA expression.

An interaction of CRHR1 rs110402 and CRHBP rs3811939 predicts high risk of comorbid AUD in schizophrenic patients (odds ratio = 2.27; 95% confidence interval, 1.56-3.30; P < .001) as well as psychiatric disease controls (odds ratio = 4.02; 95% confidence interval, 0.95-17.05; P = .06) and leads to the highest CRHR1/CRHBP messenger RNA ratio (P = .02; dysbalanced stress axis).

The high predictive value of a genetic interaction within the stress axis for the risk of comorbid AUD may be used for novel preventive and individualized therapeutic approaches.

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