BACKGROUND Despite growing evidence that e-cigarettes are likely less harmful than cigarettes, perceptions of equal or more harm have increased worldwide. This study aimed to identify the most common reasons behind adults' perceptions of the (i) relative harm of e-cigarettes compared with cigarettes and (ii) effectiveness of e-cigarettes for smoking cessation.

METHODS Adults (N = 1646) from Northern England were recruited through online panels from December-March 2017/2018, using quota sampling to guarantee socio-demographic representativeness. Qualitative content analysis of open-ended responses was performed with codes representing reasons for a given perception about e-cigarettes. Percentages of participants who gave each reason for each perception were calculated.

RESULTS 823 (49.9%) participants agreed that e-cigarettes were less harmful than cigarettes, 283 (17.1%) disagreed, and 540 (32.8%) were undecided. The most common reasons for agreeing that e-cigarettes were less harmful than cigarettes were that they produce no smoke (29.8%) and fewer toxins (28.9%). Those who disagreed were most concerned about a perceived lack of trustworthy research (23.7%) and safety issues (20.8%). Lacking knowledge (50.4%) was the most common reason for being undecided. 815 (49.5%) of participants agreed that e-cigarettes were an effective smoking cessation aid, 216 (13.2%) disagreed, and 615 (37.4%) were undecided. The most common reasons participants gave for agreeing were related to e-cigarettes being successful smoking replacements (50.3%) and advice from family, friends or health professionals (20.0%). Respondents who disagreed were most concerned about e-cigarettes being addictive (34.3%) and containing nicotine (15.3%). Lacking knowledge (45.2%) was the most common reason for being undecided.

CONCLUSIONS Negative perceptions of e-cigarette harm were driven by concerns about a perceived lack of research and safety issues. Adults who viewed e-cigarettes as ineffective for smoking cessation feared that they perpetuate nicotine addiction. Campaigns and guidelines that address these concerns may help promote informed perceptions.