Psychometric evaluation of the Self-Report Habit Index for assessing habitual e-cigarette use behavior in high school adolescents.

Background: E-cigarettes are the most-used nicotine product among adolescents, but limited psychometrically-sound, e-cigarette-relevant measures exist for adolescents. We examined psychometric properties of the Self-Report Habit Index (SRHI) for assessing adolescents' habitual e-cigarette use.

Methods: During Fall 2022, 4855 students from eight Connecticut high schools completed an anonymous survey. The analytic sample comprised 491 students who reported past-month e-cigarette use and completed the SRHI (Age M=15.94, SD=1.24 years, 56 % female, 37.1 % Hispanic, 57.6 % White). We examined the SRHI's latent factor structure; internal reliability; measurement invariance and between-groups differences (e.g., nicotine vs. nicotine-free vaping); and associations with total e-cigarette flavors used in the past month, past-30-day vaping frequency, and e-cigarette dependence.

Results: The SRHI's 6-item, 1-factor structure was confirmed. Internal reliability was excellent. The SRHI was scalar invariant for all subgroups tested. Nicotine (vs. nicotine-free) and daily (vs. non-daily) e-cigarette use were associated with greater habitual e-cigarette use behavior. In adjusted models, habitual e-cigarette use was associated with using more e-cigarette flavors, vaping more frequently, and greater e-cigarette dependence. Habitual e-cigarette use incrementally accounted for variance in past-month flavors used and vaping frequency beyond dependence.

Conclusions: The SRHI evidenced solid psychometric properties for assessing habitual e-cigarette use behavior among high school students. Relationships between habitual use and frequency of use, e-cigarette flavors, and dependence might be expected as these constructs are associated with the three characterizing features of habitual behaviors: frequent repetition, cue-driven elicitation, and automaticity. Future prospective research can clarify the temporal ordering of habitual e-cigarette use and dependence in adolescents.