Allele Polymorphism of the Serotonin Transporter Gene and Clinical Heterogeneity of Depressions

Depression disorders are a clinically heterogeneous disease group. Their development is to a substantial extent underlain by dysfunction of the serotonin system, in particular, disturbed serotonin transport. The heterogeneity of depressions is associated, among other factors, with the age at disease onset. Allele polymorphism of the serotonin transporter (5-HTT) gene was tested for association with age at disease onset, clinical signs, and anxiety-related traits of depression patients. A sample included 77 patients (mean age 61.2 ± 8.8 years) with late-onset depression (LOD, mean age at onset 56.58 ± 9.7 years) and 74 patients (mean age 31.0 ± 11.8 years) with early-onset depression (EOD, mean age at onset 23.9 ± 7.4 years). In genotype frequency distribution of two 5-HTT gene polymorphisms, the LOD and EOD groups did not differ from each other (² = 0.33, P = 0.85 for VNTR; ² = 3.33, P = 0.19 for HTTLPR) and from a control group (² = 0.34,P = 0.84 for VNTR; ² = 2.1, P= 0.35 for HTTLPR). In either group, patients differing in VNTR and HTTLPR genotypes did not differ in psychological traits and, in particular, in anxiety-related traits. In the case of the HTTLPR polymorphism, LOD patients with genotype sstended to display less severe neuroticism (t= 2.03, P = 0.0507) and scored significantly less on the Hamilton depression scale (t = 2.19, P = 0.039). Thus, the 5-HTT gene polymorphisms do not affect the risk of depression but is possibly associated with specific clinical signs of the disease, at least in elderly patients.