ObjectivesE-cigarettes are increasingly popular as smoking cessation aids. This review assessed the efficacy of e-cigarettes for smoking cessation as well as desire to smoke, withdrawal symptoms, and adverse events in adult smokers.MethodsA systematic review was conducted. Studies comparing e-cigarettes to other nicotine replacement therapies or placebo were included. Data were pooled using meta-analysis.ResultsOf 569 articles, 5 were eligible. Study participants were more likely to stop smoking when using nicotine e-cigarettes (43/489, 9 %) versus placebo e-cigarettes (8/173, 5 %); however, this difference was not statistically significant (RR 2.02; 95 % CI 0.97, 4.22). The pooled effect estimates for the desire to smoke (RR −0.22; 95 % CI −0.80, 0.36), irritability (RR −0.03; 95% CI −0.38, 0.31), restlessness (RR −0.03; 95 % CI −0.42, 0.35), poor concentration (RR −0.01; 95 % CI −0.35, 0.32), depression (RR −0.01; 95 % CI −0.22, 0.20), hunger (RR −0.01; 95 % CI −0.32, 0.30), and average number of non-serious adverse events (RR −0.09; 95 % CI −0.28, 0.46) were not statistically significantly different. Only one study reported serious adverse events with no apparent association with e-cigarette use.ConclusionsLimited low-quality evidence of a non-statistically significant trend toward smoking cessation in adults using nicotine e-cigarettes exists compared with other therapies or placebo. Larger, high-quality studies are needed to inform policy decisions.