Figure 1. Participant recruitment flowchart.

Note: See reference²³ for details on recruitment. This study analyzed data from W3 (Fall 2019) and W4, which was launched in Feb 2020 but was interrupted in mid-March to add COVID-19 related items. The W4 sample was 2,159 (71.2% of the baseline sample of 3,006); the number of participants who completed W4 after COVID-related items were added was 1,082 (69.4% of the 1,559 contacted after W4 was interrupted to add these items). W4 completers versus non-completers were older, more likely female, Asian [vs. other race], and college educated, and reported less frequent baseline use of cigarettes, e-cigarettes, and marijuana.