Abstract
<jats:p>Background: Loneliness and social isolation may contribute to tobacco and nicotine use, but existing studies have been inconsistent. This systematic review and meta-analysis examined these associations among adults amid the evolving nicotine product landscape. Methods: A systematic search of PubMed, MEDLINE, PsycINFO, and CINAHL identified peer-reviewed quantitative studies published between 2014 and 2025 searched in February-April 2026. Eligible studies included adults aged ≥18 years examining loneliness and/or social isolation in relation to smoking or nicotine use. Two reviewers independently screened studies, extracted data, and assessed risk of bias (using the National Heart, Lung, and Blood Institute risk of bias tool). Random effects meta-analyses were conducted to estimate pooled odds ratio (OR) with 95% confidence intervals (CIs). Results: 22 studies involving 273,954 participants met inclusion criteria, and 14 studies were included in the meta-analysis. A majority of the studies had low risk of bias. Meta-analysis findings showed that social isolation or loneliness was associated with significantly higher odds of nicotine product use (OR 1.84, 95% CI 1.48-2.29). Although no statistically significant association of nicotine product use and social isolation or loneliness (OR 1.35, 95% CI 0.72-2.53), some studies suggested bidirectional relationships, with smoking contributing to reduced social support and greater isolation over time. Sensitivity analysis showed the robustness of the meta-analysis findings. Subgroup analysis found no statistically significant differences were seen between subgroups defined by type of nicotine product, age groups, social isolation vs loneliness, measures of nicotine use behaviours and pre- vs post- COVID-19 pandemic period in the meta-regression. Limitations of included studies and analysis are discussed. Conclusions: Loneliness and social isolation are significant psychosocial correlates of nicotine product use. Cessation interventions may benefit from integrating social support and mental health strategies alongside traditional nicotine dependence treatment.</jats:p>