['Loneliness is one of the psychological characteristics in adolescence, during which sex hormones are elevated. The elevation of sex steroid hormones is known to sculpture and remodel neuronal circuits, which cause behavioral characteristics in adolescence. The aim of the present study is to investigate the relationship between loneliness and sex steroid hormones, testosterone (T) and 17β-estradiol (E2).', 'Fifty-eight adolescents (28 boys and 30 girls) participated in this study. The salivary levels of T and E2 were measured by Enzyme-Linked Immunosorbent Assay (ELISA). Loneliness was assessed by the UCLA loneliness scale, which is widely used as a self-administered questionnaire.', 'The results showed that Salivary E2 levels had positive relevance to loneliness in females, whereas there was no relationship in males. Salivary T level was not shown to be relevant with loneliness in either sex group.'] Does loneliness depend on salivary estradiol levels in adolescent females?