A study examined the links between childhood built environment factors and loneliness from childhood to adolescence. Conducted using data from the Adolescent Brain Cognitive Development study, researchers analyzed 8,638 children aged 9-10 over four years. They identified three loneliness trajectories: no loneliness (70.13%), transitory loneliness (27.44%), and chronic loneliness (2.43%). Key findings revealed that fewer social services, higher noise and residential density, more alcohol outlets, and greater distances from major roads were associated with transitory loneliness. In contrast, chronic loneliness was linked to non-environmental factors such as being female, having higher internalizing symptoms, and exhibiting behavioral inhibition traits. The study highlights the need for community support and urban planning that fosters social interactions and improves living conditions to support mental health in children and adolescents.