Research indicates that social isolation and loneliness increase the risk of mental disorders, but less is known about the distinct contributions of different aspects of isolation. We aimed to distinguish the pathways through which social disconnectedness (eg, small social network, infrequent social interaction) and perceptions of social isolation (eg, loneliness, perceived lack of support) contribute to anxiety and depression symptom severity in community-residing older adults aged 57-85 years at baseline.