Are quantitative targets for social network size and interaction frequency appropriate for public health guidelines on social connection? Evidence from loneliness and related mental health outcomes.

Introduction: Public health guidelines for social connection seek to address loneliness and its health consequences at the population level. Although some approaches suggest specific numeric targets (e.g., frequency of social interaction), the empirical basis for these thresholds remains unclear. We aimed to identify such thresholds for loneliness and related mental health outcomes and test their stability across strata of mental health. Methods: We analyzed repeated cross-sectional data from the Canadian Social Connection Survey collected between 2021 and 2024 (n = 1,325). Primary outcomes were emotional and social loneliness. Secondary outcomes were depressive symptoms, generalized anxiety symptoms, and self-esteem. The exposures were number of close friends and number of days in the past week spent with friends. Generalized additive models assessed non-linear associations, and segmented regression estimated approximate breakpoints if threshold emerged. Results: Significant non-linear associations were found between number of close friends and both emotional and social loneliness. Approximate breakpoints at which larger improvements stopped differed by outcome: up to 3.5 close friends for emotional loneliness and 6.7 for social loneliness. Breakpoints for larger improvements of depressive symptoms, generalized anxiety, and self-esteem ranged from 3.0 to 3.7 close friends, aligning more closely with emotional loneliness. Threshold-like patterning for days spent with friends was apparent for some secondary outcomes, but not loneliness. Stratified analyses suggested more heterogeneous patterns among participants screening positive for depression and anxiety. Conclusions: Outcome-specific breakpoints suggest potential thresholds for social connection, but variation across outcomes and population subgroups limits their interpretation as universal numeric targets or population-level guidelines.