Influence of the serotonin transporter gene on comorbid disorders among alcohol-dependent individuals.
OBJECTIVE
The role of the human serotonin transporter protein (5-HTT) gene in psychiatric disorders suggests that its variation may influence the comorbidity pattern and the heterogeneity of alcoholism. The aim of the present study is to verify possible associations between the 5-HTTLPR control region polymorphism with alcoholism and comorbid disorders.


METHODS
The polymorphic site was genotyped in 114 patients with alcohol dependence and 218 controls, all of them Brazilians of European descent. A comprehensive diagnostic interview identified the comorbid disorders.


RESULTS
Study participants with alcohol dependence and controls did not differ in the genotype and allele frequencies (genotypes: chi(2) = 2.52, P = 0.28; alleles: chi(2) = 0.37; P = 0.54). Patients with comorbid major depressive disorder (chi(2) = 6.14, P = 0.01), drug abuse (chi(2) = 6.82, P = 0.01) and nicotine dependence (chi(2) = 4.10, P = 0.04), however, presented a higher frequency of the S allele than patients without these comorbidities. Patients with comorbid depression and drug abuse also presented a higher frequency of the S allele than controls.


CONCLUSIONS
The present results are consistent with the importance of the 5-HTT gene in psychiatry. They suggest a role of the 5-HTTLPR polymorphism in a group of comorbid disorders among alcohol-dependent individuals, supporting a genetic influence in alcoholism heterogeneity.
Marques
Francine Z C
FZ
Department of Genetics, Institute of Biosciences, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
Hutz
Mara H
MH
Bau
Claiton H D
CH
D000437:Alcoholism / Q000150:complications / Q000453:epidemiology / Q000235:genetics*; D001938:Brazil; D015897:Comorbidity; D003863:Depression / Q000150:complications / Q000235:genetics; D005838:Genotype; D006801:Humans; D008297:Male; D011110:Polymorphism, Genetic; D012016:Reference Values; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*; D019966:Substance-Related Disorders / Q000150:complications / Q000235:genetics; D014029:Tobacco Use Disorder / Q000150:complications / Q000235:genetics; D044465:White People
D050486:Serotonin Plasma Membrane Transport Proteins