Season of birth variations in the temperament and character inventory of personality in a general population

Background: Since several studies show season of birth variations in morbid ity, suicidal behavior and CSF (cerebrospinal fluid) monoamine metabolites, we investigated season of birth variations in personality in the populatio n. Methods: We analyzed by multiple logistic regressions the Temperament an d Character Inventory (TCI) for 2,130 individuals taking part in the Betula prospective random cohort study of Umea, Sweden. Results: The personality dimensions were correlated significantly with age and gender. We stratified the data according to age, gender and the season of TCI measurement. By th e median split in each stratum, a high-value group and a low-value group we re obtained for each of the personality dimensions. Those born during Febru ary to April were significantly more likely than those born during October to January to have high NS (novelty seeking) among women, particularly the subscale NS2 (impulsiveness vs. reflection), and to have high PS (persisten ce) among men. Temperament profiles also showed season of birth variations. Conclusions: We discuss the associations in the literature between persona lity and the monoamines serotonin and dopamine, and suggest that our result s are compatible with a hypothesis of season of birth variation in the mono amine turnover. The personality traits are likely to be influenced by sever al genetic and environmental factors, one of them being the season of birth . Copyright (C) 2001 S. Karger AG, Basel.