In a meta-analysis, Julianne Holt-Lunstad and colleagues find that individuals' social relationships have as much influence on mortality risk as other well-established risk factors for mortality, such as smoking.

Actual and perceived social isolation are both associated with increased risk for early mortality. In this meta-analytic review, our objective is to establish the overall and relative magnitude of social isolation and loneliness and to examine possible moderators. We conducted a literature search of studies (January 1980 to February 2014) using MEDLINE, CINAHL, PsycINFO, Social Work Abstracts, and Google Scholar. The included studies provided quantitative data on mortality as affected by loneliness, social isolation, or living alone. Across studies in which several possible confounds were statistically controlled for, the weighted average effect sizes were as follows: social isolation odds ratio (OR) = 1.29, loneliness OR = 1.26, and living alone OR = 1.32, corresponding to an average of 29%, 26%, and 32% increased likelihood of mortality, respectively. We found no differences between measures of objective and subjective social isolation. Results remain consistent across gender, length of follow-up, and world region, but initial health status has an influence on the findings. Results also differ across participant age, with social deficits being more predictive of death in samples with an average age younger than 65 years. Overall, the influence of both objective and subjective social isolation on risk for mortality is comparable with well-established risk factors for mortality.

A robust body of scientific evidence indicates that being embedded in high-quality close relationships and feeling socially connected to the people in your life is associated with decreased risk for all-cause mortality as well as a range of disease morbidities. Despite mounting evidence that the magnitude of these associations is comparable to many leading health determinants (that receive significant public health resources), government agencies, healthcare providers and associations, and public/private healthcare funders are slow to recognize human social relationships as either a health determinant or health risk marker in a manner that is comparable to other public health priorities. This article evaluates current evidence (on social relationships and health) according to criteria commonly used in determining public health priorities. The piece discusses challenges for reducing risk in this area and outlines an agenda for integrating social relationships into current public health priorities. Social Relationships and Public Health

Social relationships are adaptive and crucial for survival. This review presents existing evidence indicating that our social connections to others have powerful influences on health and longevity and that lacking social connection qualifies as a risk factor for premature mortality. A systems perspective is presented as a framework by which to move social connection into the realm of public health. Individuals, and health-relevant biological processes, exist within larger social contexts including the family, neighborhood and community, and society and culture. Applying the social ecological model, this review highlights the interrelationships of individuals within groups in terms of understanding both the causal mechanisms by which social connection influences physical health and the ways in which this influence can inform potential intervention strategies. A systems approach also helps identify gaps in our current understanding that may guide future research.

Findings indicate being married per se is not universally beneficial, rather, the satisfaction and support associated with such a relationship is important. However, marriage may be distinctive, as evidence further suggests that support from one's network does not compensate for the effect of being single. These results highlight the complexities in understanding the influence of social relationships on long-term health, and they may help clarify the physiological pathways by which such associations exist.