In a study from Zachary Cahna,* and Michael Siegelb--Department of Political Science, University of California at Berkeley, and Department of Community Health Sciences, Boston University School of Public
Health
Nicotine delivery and reduction in cigarette craving
was much less than with a regular cigarette. Eissenberg20 found that
10 puffs on one brand of electronic cigarettes delivered a small
amount of nicotine, again far less than a tobacco cigarette, whereas
another brand delivered little to none. The first brand was able to
significantly reduce cigarette craving.
Taken together, this evidence suggests that electronic cigarettes are
capable of reducing cigarette craving, but that the effect is not due
exclusively to nicotine.
The entire article which is an Excellent read for any vapor is here;
http://www.hsph.harvard.edu/centers-...ticle.jphp.pdf)