Table 2

Impact of type of e-cigarette warning

	Type of warning
	(1) Control Mean (SD)	(2) Text-only Mean (SD)	(3) Pictorial Mean (SD)	1 vs 2 d	2 vs 3 d
Intended effects
Attention to message	3.20 (1.12)	3.66 (1.07)	3.70 (1.07)	0.43**	0.03
Believability	3.80 (1.00)	3.77 (1.03)	3.69 (1.00)	−0.04	−0.08
Negative affect	1.81 (.98)	2.51 (1.12)	2.75 (1.35)	0.64**	0.21**
Anticipated social interactions	2.23 (1.26)	2.55 (1.35)	2.70 (1.36)	0.24**	0.10*
Cognitive elaboration	2.25 (1.32)	3.34 (1.29)	3.49 (1.31)	0.84**	0.11*
Interest in e-cigarette use (current users only)	2.67 (.68)	2.33 (.76)	2.25 (.77)	−0.46**	−0.11
Perceived message effectiveness	2.64 (1.12)	3.48 (1.10)	3.65 (1.06)	0.76**	0.15**
Unintended effects
Message reactance	2.47 (1.06)	2.69 (1.08)	2.88 (1.12)	0.21*	0.17**
Anticipated message avoidance	2.20 (1.21)	2.57 (1.20)	2.77 (1.21)	0.30**	0.17**
Interest in cigarette use (current smokers only)	2.43 (.72)	2.32 (.73)	2.26 (.71)	−0.15*	−0.08
	%	%	%	h	h
Interest in cigarette use (non-smokers only)	8	6	6	−0.08	0.01

d, standardised mean difference; h, standardised proportion difference. Condition received text about not littering. Risk belief findings appear in online supplementary tables S2 and S3.
*p<0.05, **p<0.001.