Methods: Fifteen young adults ages 21-27, living in greater Seattle, WA (where recreational MJ is legal), and who reported past month MJ use participated in the study. They were asked to complete a brief online survey on their mobile phone or a computer about MJ use and other substance use and psychosocial factors 4 times per day for 14 consecutive days. During this period, they were also asked to carry a separate GPS data logger that obtained their geographic locations at 45-second intervals. Survey response rates and measures of adherence with carrying the GPS device were captured. Measures of exposure to MJ retail outlets and area-level poverty over time were created and linked descriptively to measures of MJ use.
Results: On average, participants completed 85% (SD = 11%) of their surveys across the 14 days. Based on daily movement (or lack thereof) patterns from the GPS data, we estimated that participants carried the GPS device on 95% of days. Exposure to a MJ retail outlet was common with participants being within 100-m of an outlet an average of 2.9 times per day (SD = 3.9). There was variability in exposure to disadvantaged areas with participants spending on average 7.1 hours per day (SD = 5.2) in census tracts in the highest tertile of area-level poverty. Cumulatively across the monitoring period, total occasions of MJ use was strongly correlated with MJ retail outlet exposure (Spearman’s rho = .6) and area-level poverty (rho = .5).
Conclusions: GEMA procedures used in this study may be promising methods to examine geospatial exposures across space and time and how they relate to MJ use and craving in young adults. Research utilizing GEMA methods could inform future novel mobile prevention interventions by targeting young adults at high-risk moments and places.