Dual use of electronic cigarettes and classic cigarettes: a systematic review

<p><b>Purpose:</b> Dual use is an emerging phenomenon and while there is no consensus on its definition, in most evidence based literature it is commonly referred to as those who use both e-cigarettes and classic cigarettes whereas those who smoke only e-cigarettes are referred to as single users. The risks and benefits of e-cigarette dual usage should be considered on an individual level as well as on a population level. Almost two thirds of adult tobacco users in the US report using more than one tobacco product. Yet, our understanding about dual use is limited by a fragmented evidence-base. Synthesizing this literature is critical for the purpose of developing a profile for ‘dual users’, understanding the influences of dual use on classic cigarette, classic cigarette smoking behavior, evaluating health outcomes from dual use, and dual users perceptions and experiences. </p> <p><b>Materials and methods:</b> The objective of this review is to summarize the literature focused on dual use of the e-cigarette and classic cigarette. PubMed and PsycINFO were searched. Concepts that made up the investigation were: electronic cigarette and dual use. The publication date was limited to 2009–2017. </p> <p><b>Results:</b> We identified 718 original studies from the electronic search of the databases (407 studies from PUBMED, and 311 from PsycINFO) and 3 from a dedicated mailing list. The reviewers screened the title and abstract of each citation to determine their eligibility and considered 76 articles. </p> <p><b>Conclusions:</b> Dual users make use of e-cigarettes for smoking reduction, smoking cessation, reduction of health risks and they perceive e-cigarettes to be safer and less addictive than tobacco cigarettes. Dual users are more likely to use tobacco cigarettes in hedonistic situations, when there is no restriction of use, or when stressed and/or anxious. Situations such as these might be the most difficult circumstances to dissuade dual users from classic smoking.</p>