Is Stress Reactivity an Intermediary Mechanism in the Association Between NR3C1 Methylation and Adolescent Loneliness?

= 0.64, 55.45% girls). Using person-centered analyses to account for interindividual differences in adolescents' stress reactivity, we identified three subgroups of cortisol responders to a social evaluative stressor: A hyporesponsive subgroup (30.5%), a moderate-responsive subgroup (44.2%), and a hyperresponsive subgroup (25.3%). Exploratory analyses also identified subgroups for two markers of the autonomous nervous system (ANS), that is, heart rate (HR) and skin conductance (SC). Furthermore, the indirect effects from NR3C1 methylation to early adolescent loneliness via individual differences in stress responses were examined. Results indicated that higher NR3C1 methylation levels were associated with a lower probability of belonging to the most reactive stress response subgroups for cortisol and HR, and to the high mean-level subgroup for SC. Additionally, higher probabilities of belonging to the low mean-level SC subgroup were associated with higher levels of loneliness. However, there was no evidence that NR3C1 methylation was associated with early adolescent loneliness, either directly or indirectly via stress reactivity. These findings highlight significant individual differences in stress reactivity, emphasizing the need to explicitly consider such variability in future research. Moreover, the results suggest that NR3C1 methylation is linked to individual differences in stress responding, warranting further investigation.