Family‐based association study of 5‐HTTLPR, TPH, MAO‐A, and DRD4 polymorphisms in mood disorders

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Abstract
Variants of the functional polymorphism in the serotonin transporter (upstream regulatory region: 5‐HTTLPR), the tryptophan hydroxylase (TPH), the monoamine oxidase A (MAO‐A), and the dopamine receptor D4 (DRD4) genes have all been associated with mood disorders. The aim of this study was to test those hypotheses by using a family‐based association approach. Both diagnoses and psychopathology were used for phenotype definitions. A total of 134 nuclear families with mood disorders, with probands affected by bipolar (n = 103) or major depressive (n = 58) disorders, were included in the study. All subjects were typed for the above‐mentioned gene variants using polymerase chain reaction (PCR) technique. No significant transmission disequilibrium was found in the overall sample for any polymorphism. A separate analysis of bipolar subjects only, or the use of continuous psychopathologic traits as affectation status did not influence the observed results. Our study did not support the involvement of 5‐HTTLPR, TPH, MAO‐A, or DRD4 polymorphisms in mood disorders.