Analysis of Serotonin Transporter Gene 5-HTTLPR Polymorphism and Its Impact on Personality Traits in a Sample Without Neuropsychiatric or Substance Use Disorders

Variations within the serotonin transporter gene, <i>SLC6A4</i> (solute carrier family 6 member 4), particularly the <i>5-HTTLPR</i> (serotonin-transporter-linked promoter region), have been extensively studied in relation to behavioral and psychological traits. The aim of our study is to examine the relationship between the <i>5-HTTLPR</i> polymorphism located in the <i>SLC6A4</i> gene and personality traits, as assessed using the NEO-FFI (NEO Five Factor Inventory). The MANOVA model demonstrated a significant overall association, accounting for approximately 8% of the variance in the data (Wilk's λ = 0.847, F_10,342 = 2.979, <i>p</i> = 0.0013, η² = 0.08). Subsequent ANOVAs revealed statistically significant <i>5-HTTLPR</i> polymorphism associations with the Neuroticism (<i>p</i> = 0.0018, R² = 0.070), Openness (<i>p</i> = 0.0364, R² = 0.037), and Conscientiousness (<i>p</i> = 0.0020, R² = 0.068) dimensions. The post-hoc analysis revealed that individuals with the LL genotype obtained significantly lower Neuroticism scores compared to the S/S (<i>p</i> = 0.0011) and SL genotype (<i>p</i> = 0.0086) carriers. Similarly, individuals with the L/L genotype had lower Openness scores compared to those with SS genotype (<i>p</i> = 0.0107). LL and SL genotype carriers had higher Conscientiousness scores compared to those with the SS genotype (<i>p</i> = 0.0004 and <i>p</i> = 0.0109, respectively). In conclusion, our study provides further data regarding the implications of <i>5-HTTLPR</i> polymorphism in the complex genetic architecture of human personality. The observed associations with Neuroticism, Openness, and Conscientiousness, while modest in effect size, contribute to our understanding of how genetic variation at the <i>SLC6A4</i> locus may subtly shape individual personality differences.