The role of social media influencer promotion in initiation and use of cigar, little cigar, cigarillo, and cannabis products among US youth and young adults: Using exogenous marketing exposure measures.

BACKGROUND: Influencer marketing on social media is a powerful, yet under-examined, driver of youth and young adult substance use. Yet, reliably identifying influencer promotion and measuring its effects, particularly at community level, remains challenging. Influencers rarely disclose brand relationships, and conventional self-reported exposure metrics fail to capture the complex digital media environment and are vulnerable to recall and endogeneity biases. This study overcomes these limitations by employing exogenous localized measures of cigar, little cigar, and cigarillo (CLCC) influencer marketing to examine the effects of influencer messages on health behavior. METHOD: A corpus of over 48 million geolocated tweets was compiled using a combination of machine learning and human coding methods and integrated with retrospective data from a nationally representative survey of US individuals aged 15-21 (n = 9,555). Seven distinct metrics (including simple descriptive and network-based measures) were used to identify and quantify influential accounts that posted about CLCCs. County-level influencer tweet measures within four weeks before taking the survey were linked with the respondents' CLCC and cannabis use. RESULTS: Multivariate logistic regression analyses revealed that living in a county with any tweets from high-follower influencers was associated with 70% greater odds of current CLCC use (OR = 1.70) and 79% greater odds of current cannabis use (OR = 1.79). Among non-current users at baseline, potential exposure to high-follower influencers' tweets was associated with 263% greater odds of initiating current CLCC use by follow-up (OR = 3.63). CONCLUSIONS: These findings indicate that county-level influencer marketing is associated with CLCC and cannabis use and initiation, and demonstrates spillover effects from tobacco to cannabis promotion. This work showcases a novel method for identifying social media influencers and assessing the effects of exposure to their posts on health behavior.