Neighborhood, social isolation and mental health outcome among older people in Ghana.

•About 74% of the lonely lived alone but some 66% who co-resided with others felt lonely.•Loneliness and living alone were independently and interactively associated with higher mental health risk.•Unlike living alone, the impact of loneliness was highly differentiated and increased with age.•Physical activity and social connectedness buffered against the effects of loneliness and living alone on mental disorders.•Mental health promotion agendas in later life should include physical activity and social cohesion interventions.