Thyroid Hormones Role in Neuroticism Formation and Aggression Development

Abstract

Excessive aggression has negative consequences for both individuals and society. According to some literature data, both high impulsive and premeditated aggressions are associated with high neuroticism. The association between blood serum levels of thyroid hormones and cortisol, neuroticism and physical aggression in men was studied. No correlation between thyroid hormones and physical aggression was found both in total group and in individuals with high and middle levels of neuroticism, but in persons with high neuroticism level, the involvement of thyroid hormones into prediction of physical aggression was revealed by multiple stepwise regression analysis. In men with high neuroticism level, the significant positive correlations between neuroticism and thyroxine (r=+0.78, p=0.008), between thyroxine and cortisol (r=+0.77, p=0.009) were observed, and the involvement of thyroid hormones and cortisol into prediction of physical aggression was revealed by multiple stepwise regression analysis. In men with middle neuroticism level no correlation between investigated parameters was found. Persons with high and middle levels of neuroticism didn’t differ in cortisol and thyroid hormones levels, but difference in thyroxine level was almost significant (high neuroticism level – 146.72 [115.83, 169.69], middle neuroticism level 119.69 [101.67, 135.90], p=0.079). In men with high neuroticism level it was higher than in individuals with middle neuroticism level. Obtained data indicate the necessity of participants division depending on expression degree of personality traits to study the mechanisms of aggression development. Thyroid hormones and cortisol are involved in the formation of high level of neuroticism, which is confirmed by the results of multiple stepwise regression analysis, by the existence of significant positive correlations between neuroticism and thyroid hormones, between thyroid hormones and cortisol together with our early published data about correlation between neuroticism and cortisol in individuals with high neuroticism level. In persons with high neuroticism level, thyroid hormones are indirectly involved in aggression development due to the results of multiple stepwise regression analysis, and significant positive correlation between neuroticism and physical aggression in these individuals.