ABSTRACTIntroductionCOVID‐19 has resulted in major life changes to the majority of the world population, particularly adolescents, with social‐distancing measures such as home‐based schooling likely to impact sleep quality. Increased worry is also likely considering the substantial financial, educational and health concerns accompanying COVID‐19. White matter (WM) integrity has been shown to be associated with anxiety and depression symptoms, including worry, as well being closely associated with sleep quality. This study aimed to investigate the associations between pre‐COVID sleep quality, WM structural integrity and levels of worry and rumination about COVID.MethodsN = 30 adolescent participants from Queensland, Australia, completed diffusion tensor imaging (DTI) scanning pre‐COVID, the Pittsburgh Sleep Quality Index (PSQI) pre and during COVID, and 9 items designed to measure 3 constructs, perceived impact of COVID, general worry, and COVID‐specific worry and rumination.ResultsSleep quality (PSQI total) was significantly poorer during COVID compared with pre‐COVID. Sleep onset latency measured pre‐COVID was significantly associated with COVID‐specific worry and rumination. While the structural integrity of a number of WM tracts (measured pre‐COVID) were found to be significantly associated with COVID‐specific worry and rumination. Follow‐up regression analysis using a model including pre‐COVID sleep onset latency, structural integrity of the posterior limb of the internal capsule (PLIC), gender and change in PSQI explained a significant 47% of the variance in COVID‐specific worry and rumination.ConclusionsThese findings suggest that adolescents with poor sleep quality and perturbed WM integrity may be at risk of heightened reactivity to future stressful events and interventions should focus on improving sleep onset latency.