Association of internet addiction symptoms with hair cortisol and hair testosterone concentrations

Internet addiction (IA) has been consistently shown to be closely associated with stress; however, studies on physiological stress in IA have yielded mixed findings regarding the relationship between IA and cortisol. In addition, the role of testosterone-another hormone potentially relevant to addiction-has been scarcely examined in IA. The present study investigated associations between IA symptom severity and long-term basal secretion of cortisol and testosterone using hair-based hormone measures. A total of 155 Japanese undergraduate and graduate students (94 females, mean age = 21.1 years, standard deviation = 4.1 years) participated in the study. IA symptom severity was assessed using the Japanese version of the Internet Addiction Test (Osada, 2013; Young, 1998). Hair cortisol and hair testosterone concentrations, reflecting cumulative hormone secretion over the preceding three months, were quantified using enzyme-linked immunosorbent assays. A multivariate linear regression analysis revealed that hair cortisol concentrations were negatively associated with IAT scores, whereas hair testosterone concentrations were not. These results suggest that IA symptom severity may be linked to altered long-term activity of the hypothalamic-pituitary-adrenal axis. By jointly examining cortisol and testosterone, the present findings extend previous research that has largely focused on single hormonal systems.