General-Purpose LLM Chatbots as Informal Step-0 Support: Systematic Review and Meta-analysis of Human–Human Social Connectedness Outcomes (Preprint)

Abstract

<sec> <title>BACKGROUND</title> General-purpose artificial intelligence (AI) chatbots powered by large language models (LLMs) are increasingly used as always-available sources of companionship, advice, and emotional support. In real-world practice, this pattern can position everyday chatbots as a de facto “step 0” within emerging stepped-care ecosystems. However, the evidence base has emphasized symptoms and usability more than interpersonal processes, and it remains unclear whether AI-human interaction strengthens or erodes human–human social connectedness (eg, loneliness, perceived social support, interpersonal communication, empathy), outcomes that are plausibly proximal to disclosure and downstream help-seeking. </sec> <sec> <title>OBJECTIVE</title> This systematic review and meta-analysis aimed to synthesize quantitative evidence on the association between LLM chatbot interaction and human–human social connectedness across populations and study designs, and to identify measurement gaps that constrain inference about safe stepped-care integration. </sec> <sec> <title>METHODS</title> We conducted a PRISMA- and MOOSE-guided systematic review (PROSPERO registered) of studies published from January 1, 2022 onward. Searches were conducted in PubMed, Web of Science, Scopus, and PsycINFO, with an updated search in June 2025. We included quantitative and mixed-method/intervention studies in which LLM chatbot interaction was the primary exposure and social connectedness–related constructs were outcomes. Studies of embodied agents and legacy voice assistants were excluded. Two reviewers screened and extracted data, and risk of bias was assessed using the Newcastle-Ottawa Scale. We conducted three-level generic inverse-variance meta-analyses to pool effects separately for experimental/intervention studies (Cohen d) and cross-sectional studies (standardized β), with meta-regression testing moderation by participant sex (percentage male). </sec> <sec> <title>RESULTS</title> From 5302 records, 8 studies were eligible for meta-analysis (4 experimental/intervention; 4 cross-sectional). Experimental/intervention studies (174 participants) showed a large positive effect of AI-human interaction on social connectedness outcomes (Cohen d=1.29, 95% CI 1.06-1.51; k=11 effect sizes), with substantial heterogeneity (I²=70.1%). Cross-sectional studies (3325 participants) showed no statistically significant association between LLM chatbot use and social connectedness (β=-0.10, 95% CI -0.75 to 0.55; k=12), with extreme heterogeneity (I²=99.8%). Sex did not significantly moderate effects. Sensitivity analyses indicated that the pooled experimental effect was highly contingent on individual studies. </sec> <sec> <title>CONCLUSIONS</title> Structured, purpose-built AI-supported interactions can improve social connectedness–related outcomes under controlled conditions, but current evidence does not support assuming that every day, naturalistic chatbot use reliably enhances real-world human connectedness. Crucially for stepped-care framing, none of the included studies assessed help-seeking intentions or behavior, nor transitions from chatbot use to human sources of support, limiting inference about escalation, substitution, or safe “step 0” implementation. Future work should prioritize longitudinal and stepped-care designs with standardized interpersonal outcomes and validated help-seeking/escalation measures to determine whether everyday AI use augments human support or increases substitution risk. </sec> <sec> <title>CLINICALTRIAL</title> PROSPERO registration number: CRD42022325540 </sec>

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