Box 1. Penn State [Electronic] Cigarette Dependence Index

[For the Electronic Cigarette Dependence Index, substitute the underlined word with the words in square brackets]1. How many cigarettes [times] per day do you usually smoke [use your electronic cigarette]?a ([assume that one “time” consists of around 15 puffs or lasts around 10 minutes]) (Scoring: 0–4 times/day = 0, 5–9 = 1, 10–14 = 2, 15–19 = 3, 20–29 = 4, 30+ = 5)

2. On days that you can smoke [use your electronic cigarette] freely, how soon after you wake up do you smoke your first cigarette of the day [first use your electronic cigarette]?a (Scoring: 0–5 mins = 5, 6–15 = 4, 16–30 = 3, 31–60 = 2, 61–120 = 1, 121+ = 0)

3. Do you sometimes awaken at night to have a cigarette [use your electronic cigarette]?b (Scoring: Yes = 1, No = 0)

4. If yes, how many nights per week do you typically awaken to smoke [use your electronic cigarette]?b (Scoring: 0–1 nights = 0, 2–3 nights = 1, 4+ nights = 2)

5. Do you smoke [use an electronic cigarette] now because it is really hard to quit?c (Scoring: Yes = 1, No = 0)

6. Do you ever have strong cravings to smoke [use an electronic cigarette]?c (Scoring: Yes = 1, No = 0)

7. Over the past week, how strong have the urges to smoke [use an electronic cigarette] been?d (Scoring: None/Slight = 0, Moderate/Strong= 1, Very Strong/Extremely Strong = 2)

8. Is it hard to keep from smoking [using an electronic cigarette] in places where you are not supposed to?c (Scoring: Yes = 1, No = 0)

When you haven’t used tobacco [an electronic cigarette] for a while or when you tried to stop smoking [using]… 9. Did you feel more irritable because you couldn’t smoke [use an electronic cigarette]?c (Scoring: Yes = 1, No = 0)

10. Did you feel nervous, restless, or anxious because you couldn’t smoke [use an electronic cigarette]?c (Scoring: Yes = 1, No = 0)

Total scoring: 0–3= not dependent, 4–8 low dependence, 9–12 medium dependence, 13+ = high dependence.

The original questionnaire asks about cigarette use and electronic cigarette use separately, and the wording for e-cig questions is provided here in brackets merely to facilitate comparisons and save journal space.

^aFrom FTND/HSI.

^bFrom Bover et al. ¹⁶

^cFrom Hooked on Nicotine Checklist.

^dFrom Fiddler et al. ¹⁸