LAUSR

Social withdrawal may lead to mental health problems and can have a large impact on a life course, particularly among boys. To support adolescents with social withdrawal, an integrative understanding of the biological bases would be helpful. Social dominance, a possible opposite of social withdrawal, is known to have positive associations with testosterone levels. A previous study suggested that social withdrawal has a negative relationship with sexual maturity among adolescent boys. However, the relationship between social withdrawal and testosterone in adolescence is unknown. This study aimed to examine whether social withdrawal was negatively associated with testosterone levels in early adolescent boys. Salivary samples were collected from 159 healthy early adolescent boys (mean age [standard deviation]: 11.5 [0.73]) selected from participants of the "population-neuroscience study of the Tokyo Teen Cohort" (pn-TTC). Social withdrawal and confounding factors, such as the secondary sexual characteristics and their age in months, were evaluated by self-administered questionnaires completed by the primary parents. The degree of social withdrawal was assessed with the Child Behaviour Checklist (CBCL). Levels of salivary testosterone, and cortisol as a control, were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Logistic regression was conducted to examine the association between social withdrawal and testosterone levels. A higher risk of social withdrawal was associated with a lower salivary testosterone level after adjustment for age in months (odds ratio 0.55, 95 % confidence interval 0.33-0.94), and the association remained significant after adjusting for body mass index, the degree of anxiety/depression and pubertal stage. Thus, we found a negative relationship between social withdrawal and testosterone levels in early adolescent boys. These findings may help to clarify the biological foundations of and to develop support for social withdrawal.