Evidence base
PLoS Medicine
Social Relationships and Mortality Risk: A Meta-analytic Review
What it found
This 2010 meta-analysis pooled 148 studies covering 308,849 participants and found that stronger social relationships were associated with a 50% increased likelihood of survival over the follow-up periods studied. The authors report this effect size as comparable in magnitude to other well-established mortality risk factors.
Why it matters for practice
This is the reference point most social prescribing and connection-focused interventions cite to justify their premise; if you are building a case for funding or programme design, know that it establishes association across a large pooled sample, not causation, and it does not tell you which types of intervention reliably increase relationship strength.