% % % Difference (95% CI)
 Awareness of
   Chemicals in intervention messages§35915.036028.113.01 (7.08 to 18.95)<0.001
   Health effects in intervention messages§35951.836060.38.47 (1.24 to 15.70)0.02
   Chemicals not in intervention messages§35916.236013.6−2.54 (−7.75 to 2.66)0.34
   Health effects not in intervention messages§35948.236043.9−4.30 (−11.58 to 2.98)0.25
 Made quit attempt (for 24 hours) in the past 3 weeks35941.836041.4−0.39 (−7.60 to 6.81)0.92
 Quit smoking for ≥7 days3597.03605.8−1.13 (−4.71 to 2.45)0.54
  • Outcomes were assessed by survey at the final trial visit.

  • *Response scale for quit intentions ranged from 1 to 4, with 4 indicating highest intentions.

  • †Response scale for negative affect, thinking about the chemicals in cigarettes, thinking about the harms of smoking, thinking about the message, thinking about quitting and perceived likelihood of harm from smoking ranged from 1 to 5, with 5 indicating higher quantity or stronger endorsement.

  • ‡Negative affect and thinking about the message were not assessed until week 3 follow-up, resulting in a smaller n for these analyses.

  • §Had heard of at least half of the chemicals being in cigarette smoke or their health effects, in a 2-to-4-item index.