First- versus second-generation electronic cigarettes: predictors of choice and effects on urge to smoke and withdrawal symptoms.

Aims: To (1) estimate predictors of first- versus second-generation electronic cigarette (e-cigarette) choice; and (2) determine whether a second-generation device was (i) superior for reducing urge to smoke and withdrawal symptoms (WS) and (ii) associated with enhanced positive subjective effects.

Design: Mixed-effects experimental design. Phase 1: reason for e-cigarette choice was assessed via questionnaire.