Currently submitted to: Journal of Medical Internet Research
Date Submitted: Oct 5, 2026
Open Peer Review Period: Oct 6, 2026 - Dec 1, 2026
(currently open for review)
Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.
Effectiveness of social media recruitment to a large web-based population cohort study: An observational analysis
ABSTRACT
Background:
Rising global social media use offers health researchers new ways to reach large, diverse populations. However, few studies have assessed the effectiveness of social media advertising for recruiting into longitudinal, population-based cohorts with broad eligibility criteria. Building on prior findings that social media recruitment is scalable and cost-effective in comparison to other methods, we evaluated the effectiveness of social media advertising, including paid agency delivered material, to inform future tailored recruitment strategies.
Objective:
The objective of this study was to compare the sociodemographic characteristics of participants > 16 years recruited via social media into an extension of the Generation Scotland longitudinal cohort (‘NextGenScot’) with the general Scottish population. Second, to use engagement and conversion metrics to assess the performance of platforms and advertisement styles in a responsive, real-world recruitment setting.
Methods:
Recruitment to NextGenScot ran from May 2022-June 2025 with broad eligibility (anyone aged > 12 years living in Scotland). Multiple recruitment channels were used, including paid agency-led campaigns on Meta (Facebook/Instagram), TikTok, Snapchat and YouTube. Recruitment routes were determined through self-report questionnaire. Platform and advertisement performance were assessed using click-through rate (CTR), cost per click (CPC), and estimated sign-ups.
Results:
Of N=13,619 NextGenScot participants >16 years, N=6,705 (49.2%) reported recruitment via social media. Compared with the Scottish population, social media recruits were more likely to be female (80.5% vs 51.9%) and older (41.7% vs 30.8% > 60 years), while socioeconomic and geographic representation broadly matched population estimates. Facebook had the highest CTR (0.87%) and estimated sign-ups. Snapchat generated the most impressions and lowest CPC (£0.04). A professionally produced TV-style advert adapted for social media generated the most sign-ups, and short-form video outperformed image-based ads.
Conclusions:
Social media, including a paid reactive approach, was an effective and adaptable recruitment tool, achieving broad geographic and sociodemographic coverage. Findings highlight the potential of responsive social media approaches to support recruitment into large-scale research studies. Clinical Trial: NA
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