AbstractObjectiveThe COVID-19 pandemic dramatically altered social determinants of health including work, education, social connections, movement, and perceived control; and loneliness was commonly experienced. This longitudinal study examined how social determinants at the personal (micro), community (meso), and societal (macro) levels predicted loneliness during the pandemic.MethodsParticipants were 2056 Australian adults surveyed up to three times over 18 months in 2020 and 2021. Multi-level mixed-effect regressions were conducted predicting loneliness from social determinants at baseline and two follow-ups.ResultsLoneliness was associated with numerous micro determinants: male gender, lifetime diagnosis of a mental health disorder, experience of recent stressful event(s), low income, living alone or couples with children, living in housing with low natural light, noise, and major building defects. Lower resilience and perceived control over health and life were also associated with greater loneliness. At the meso level, reduced engagement with social groups, living in inner regional areas, and living in neighbourhoods with low levels of belongingness and collective resilience was associated with increased loneliness. At the macro level, increased loneliness was associated with State/Territory of residence.ConclusionsTherapeutic initiatives must go beyond psychological intervention, and must recognise the social determinants of loneliness at the meso and macro levels.