Table 1.

Penn state electronic cigarette dependence index score and individual components.

Mean PSECDI Score (SD)	7.8 (4.2)
% (n) No Dependence	15.8 (12)
% (n) Low dependence	46.1 (35)
% (n) Medium dependence	23.7 (18)
% (n) High dependence	14.5 (11)
Mean times per day (SD) (Range)	9.5 (11.0) (1–48)
Mean time to first use on waking(in mins) (SD) (Range)	62.6 (100.5) (0–700)
% (n) Awaken at night to use	11.8 (9)
% (n) Use e-cig because it is really hard to quit	44.7 (34)
% (n) Have strong cravings to use e-cig	72.4 (55)
% (n) With very or extremely strong urges to use	9.2 (7)
% (n) Find it hard to keep from using in places where you are not supposed to	34.2 (26)
% (n) More irritable when they cannot use	54.0 (41)
% (n) More nervous when they cannot use	52.6 (40)