Health care workers, as well as society at large, recognize that social isolation and loneliness (SI/L) are major public health concerns in higher-income countries. Almost one-fourth of community-dwelling older adults are socially isolated, while 35% of adults 45 years and older report feeling lonely.1,2 Social isolation and loneliness increase mortality risk. Nearly 4 decades of research have produced robust evidence that scoring high on measures of social isolation in later life is associated with a significantly increased risk (25%) for premature mortality from all causes in controlled studies.3,4 The evidence is not as strong for loneliness, but it is mounting. However, empirical data informing the biological mechanisms of and interventions to reduce these conditions are negligible given the significance of the problem. Evidence-based interventions are almost nonexistent. For these reasons, the AARP Foundation commissioned the National Academies of Science, Engineering, and Medicine (NAM) to study the medical dimensions of and interventions for SI/L in persons 50 years or older. In this Viewpoint, I review the findings of the report,5 focusing on how these findings apply to mental health workers.