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. Author manuscript; available in PMC: 2021 Feb 5.
Published in final edited form as: JAMA Netw Open. 2020 Feb 5;3(2):e1921513. doi: 10.1001/jamanetworkopen.2019.21513

Table 1.

Participant Characteristics in Overall Sample and Stratified by e-Cigarette Dependence Symptom Status at Baseline

Youths, No. (%) [Total Respondents, No.]
e-Cigarette Dependence Symptoms Reported
Variable Overall Sample (N = 444) 0 (n = 392) ≥1 (n = 52) P Value for Contrasta
Female 217 (48.9) [444] 194 (49.5) [392] 23 (44.2) [52] .55
Age, mean (SD), y 17.48 (0.39) [444] 17.47 (0.37) [392] 17.54 (0.49) [52] .23
Race/ethnicity
 Hispanic 187 (42.9) [436] 168 (43.8) [384] 19 (36.5) [52] .61
 Asian 76 (17.4) [436] 68 (17.7) [384] 8 (15.4) [52]
 African American 14 (3.2) [436] 11 (2.9) [384] 3 (5.8) [52]
 White 87 (20.0) [436] 74 (19.3) [384] 13 (25.0) [52]
 Otherb 72 (16.5) [436] 63 (16.4) [384] 9 (17.3) [52]
Parents graduated collegec 207 (52.3) [396] 181 (51.6) [384] 26 (57.8) [45] .53
Age at e-cigarette use onset, mean (SD), y 15.31 (1.58) [440] 15.33 (1.55) [388] 15.15 (1.81) [52] .43
Any past 6-mo e-cigarette use 265 (60.1) [441] 224 (57.4) [390] 41 (80.4) [51] .001
Past 30-d, mean (SD)
 Nicotine vaping days, No. 1.74 (5.71) [441] 1.17 (4.35) [390] 6.10 (10.85) [51] <.001
 Nicotine vaping sessions/d, No. 1.55 (4.43) [438] 1.05 (3.60) [386] 5.25 (7.42) [52] <.001
 Puffs per nicotine vaping sessions, No. 1.42 (3.83) [440] 0.96 (2.89) [388] 4.87 (7.04) [52] <.001
Age at combustible cigarette use onset, mean (SD), y 15.04 (2.34) [226] 15.14 (2.22) [194] 14.45 (2.95) [32] .12
Any past-year combustible cigarette smoking 146 (32.9) [444] 122 (31.1) [392] 24 (46.2) [52] .04
Past 30-d, mean (SD)
 Cigarette smoking days, No. 1.19 (4.64) [438] 1.06 (4.57) [387] 2.16 (5.07) [51] .11
 Cigarettes smoked/d, No. 0.49 (2.19) [436] 0.39 (1.85) [385] 1.29 (3.81) [51] .005
Ever use cigar, hookah, or smokeless tobacco 287 (65.2) [440] 244 (62.7) [389] 43 (84.3) [51] .002
Ever substance use
 Alcohol 402 (91.8) [438] 353 (91.2) [387] 49 (96.1) [51] .41
 Smoked cannabis 340 (77.8) [437] 296 (76.7) [386] 44 (86.3) [51] .15
 Vaped cannabis 212 (48.3) [439] 180 (46.4) [389] 32 (62.7) [51] .04
 Other drugsd 241 (54.8) [440] 207 (53.2) [388] 34 (66.7) [51] .07
Mental health symptoms, mean (SD), No.
 Conduct problemse 15.93 (6.88) [426] 15.60 (6.34) [376] 18.34 (9.85) [50] .008
 ADHDf 12.53 (10.20) [427] 12.26 (9.83) [376] 14.50 (12.49) [51] .14
 Social phobiag 9.25 (7.29) [433] 9.10 (7.17) [382] 10.33 (8.10) [51] .26
 Major depressive disorderg 8.16 (7.23) [433] 7.65 (6.97) [382] 11.92 (8.03) [51] <.001
 Generalized anxiety disorderg 6.91 (4.70) [435] 6.74 (4.70) [384] 8.20 (4.60) [51] .04
 Maniah 5.44 (3.68) [438] 5.23 (3.64) [387] 7.04 (3.61) [51] .001
 Panic disorderg 4.24 (5.31) [436] 4.05 (5.14) [384] 5.63 (6.28) [52] .04
 Obsessive-compulsive disorderg 3.19 (3.33) [439] 3.08 (3.29) [387] 4.02 (3.57) [52] .06

Abbreviations: ADHD, attention-deficit/hyperactivity disorder; e-cigarette, electronic cigarette.

a

Calculated using the χ2 test for categorical variables and 1-way analysis of variance for continuous variables.

b

Includes American Indian or Alaskan Native, Native Hawaiian or Pacific Islander, multiethnic or multiracial, or other.

c

Excludes 48 youths who did not respond to the survey question or who marked don’t know.

d

Includes inhalants, cocaine, methamphetamine, lysergic acid diethylamide (LSD), ecstasy, heroin, salvia, prescription pain medications, tranquilizers or sedatives, diet pills, prescription stimulants, and bath salts.

e

Calculated by summing scores (range, 11–66) for 11 delinquent behaviors indicative of conduct problems over the past 6 months; each behavior is rated from 1 (never) to 6 (10 or more times), with higher scores indicating greater frequency of engaging in these behaviors.

f

Symptom sum score of ADHD symptoms self-rating scale (range, 0–54); higher scores indicate more frequent ADHD symptoms in the past 6 months.

g

Symptom sum scores from the Revised Child Anxiety and Depression Scales major depressive disorder (range, 0–30), generalized anxiety disorder (range, 0–18), panic disorder (range, 0–27), social phobia (range, 0–27), and obsessive-compulsive disorder (range, 0–18) subscales; higher scores indicate more severe mental health symptoms.

h

Symptom sum from the 15-item Mood Disorder Questionnaire (range, 0–13); higher scores indicate more past-year mania symptoms.