LAUSR

INTRODUCTION The COVID-19 pandemic disrupted the daily social lives of adolescents by severely limiting social interactions which likely heightened levels of loneliness and a variety of internalizing symptoms. However, little is known about how social distancing adherence and subsequent stress caused by the novel social regulations impact adolescents' feelings of loneliness, and later mental health difficulties, including anxiety and depression. METHOD To close this gap, we examined the impact of social distancing regulations on adolescents' (N = 79; Mage  = 16.16, SD = 1.15; 47 females; 23 males) depression and anxiety symptoms through loneliness by using data from a 5-week longitudinal study conducted on adolescents in the United States during the initial phases of COVID-19. RESULTS AND CONCLUSIONS Findings provided evidence that loneliness plays a unique mediating link between social distancing and symptoms of anxiety and depression. Overall, the present study highlights how social distancing during the COVID-19 pandemic has impacted adolescents' mental health during a developmental period that is considered a turning point for psychopathology.