Association of the s allele of the 5-HTTLPR with neuroticism-related traits and temperaments in a psychiatrically healthy population

Research concerning the genetic background of traits, temperaments and psychiatric disorders has been rapidly expanding. One of the most frequently studied genetic polymorphisms in the background of psychological and psychiatric phenomena is the 5-HTTLPR polymorphism of the serotonin transporter gene which has earlier been found to be associated with neuroticism and neuroticism-related traits and disorders. However, both the neuroticism trait and psychiatric disorders are complex and composed of several subfacets. The aim of our study was to investigate the association of the 5-HTTLPR polymorphism with several smaller, distinct and better characterisable phenomena related to the neuroticism trait. 169 healthy females participated in the study. All participants completed the Buss-Durkee Hostility Inventory (BDHI), the State-Trait Anxiety Inventory (STAI), The Zung Self-rating Depression Scale (ZSDS), the Beck Hopelessness Scale, the SCL-51, the Temperament and Character Inventory (TCI) and the Temperament Evaluation of Memphis, Pisa, Paris and San Diego (TEMPS-A) questionnaire. All subjects were genotyped for the 5-HTTLPR using PCR. Data were analysed with ANOVA and MANCOVA with age as a covariate. We found that the presence of the s allele was significantly associated with anxiety, depression, hopelessness, guilt, hostility, aggression, presence of neurotic symptoms, self-directedness and affective temperaments carrying a depressive component even when controlling for age. Our study is the first that confirms that traits and characteristics related to neuroticism, such as increased anxiety, depression, hopelessness, somatization, feeling of guilt, hostility, aggression, lack of self-directedness and affective temperament are consistently and independently associated with the 5-HTTLPR polymorphism of the serotonin transporter gene. Our study therefore suggests that neuroticism can be considered a unified construct not only from a phenotypical but also from a genetic point of view and 5HTTLPR can be considered one component of its polygenic background. Our results thus yield further insight into the role of the 5-HTTLPR in the background of neuroticism and neuroticism-related psychiatric disorders.