After reading posts regarding e-cig users blood levels of nicotine and continine ( just slightly higher than a non-smokers), IMO, much of the sleeplessness, as well as headaches, jitters, etc in new vapers ( me included, going on my 6th week vaping around 3 mills a day of 24mg) is likely due to PG being converted to lactic acid, rather than nicotine. The metabolic effects of so much lactic acid in your system are unknown, as well as likely varying from individual to individual ( depending on a number of factors). And if you are off the analogs, there is one big factor rarely discussed, namely your blood gases will no longer feature a high level of carbon monoxide.