Impact of loneliness on diurnal cortisol in youth.

Loneliness is associated with multiple forms of psychopathology in youth. However, we do not yet know how loneliness gets "under the skin" in ways that may impact the long-term health and development of early adolescents. In particular, loneliness may influence youths' patterns of diurnal cortisol, an index of hypothalamic-pituitary-adrenal (HPA) axis functioning and a central predictor of health across the lifespan. The current severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2, or COVID-19) pandemic represents a salient period in which to study the consequences of loneliness, as recent work has provided evidence that the physical-distancing measures put in place to contain the virus have resulted in greater loneliness, particularly among youth. Thus, the current study aimed to examine the prospective association between loneliness during the COVID-19 pandemic and diurnal cortisol in early adolescents. We found that greater loneliness was associated with higher levels of cortisol at waking and a blunted cortisol awakening response (CAR). These results held even when controlling for covariates that can influence diurnal trajectories of cortisol. Critically, this pattern of HPA-axis functioning increases risk for adverse mental and physical health outcomes across adolescence and into adulthood. This study is the first to examine the prospective association between loneliness and diurnal cortisol in early adolescence, and the first to identify mechanisms that contribute to biological markers of distress during the COVID-19 pandemic. Findings underscore the importance of developing and distributing strategies to mitigate feelings of loneliness among youth.