The aim of this study was to determine whether the serotonin transporter gene polymorphism (5-HTTLPR) is associated with the treatment outcomes of escitalopram for patients with comorbid major depression and alcohol dependence. Eighty treatment-seeking patients were randomly assigned to either receive 20mg of escitalopram or a control of 20mg of the non-serotonergically acting memantine. Depression was measured by the Montgomery-Asberg Depression Rating Scale (MADRS) and alcoholism by the Alcohol Use Disorders Identification Test (AUDIT). Twenty-nine participants in each treatment group completed the study, and from those DNA was given by 27 in the escitalopram group and 21 in the memantine group. In the escitalopram group linear regression showed that LL genotype predicted greater decrease in MADRS scores compared with the SS/SL genotypes (p=0.04) after a 3month treatment period. Moreover, each L allele associated with MADRS score decrease by 15% (p=0.04) in the escitalopram group. In the memantine group, however, no association between LL genotype and MADRS decrease was detected. AUDIT decrease was not associated with the 5-HTTLPR genotype for either medication. This is the first study in the treatment of depression in dual diagnosis patients to report a significant association between outcomes with escitalopram and the 5-HTTLPR gene polymorphism.
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