Table 4 Multivariable Poisson regression (with robust variance) analysis of variables related to high WPS dependence

Age(Ref: ≤20 years)

0.996

0.98–1.01

0.509

Gender(Ref: Female)

0.97

0.93–1.12

0.229

Time spent with friends a day(Ref: Less than 2 h)

 2–5 h

0.99

0.93–1.11

0.843

 More than 5 h

1.12

0.97–1.47

0.497

College(Ref: Humanities)

 Sciences-nonmedical

0.98

0.94–112

0.395

 Sciences-medical sciences

1.13

1.10–1.18

0.037

Cigarette smoker(Ref: No)

1.18

1.12–1.25

0.008

Vape smoker(Ref: No)

1.05

0.97–1.14

0.795

Number of WPS per week(Ref: Less than once)

 1–2 times

1.28

1.20–1.56

< 0.001

 3–6 Times

1.43

1.30–1.64

< 0.001

 ≥ 7 times

1.98

1.39–2.32

< 0.001

Percent of daily allowance spent on WPS(Ref: ≤10% of daily allowance)

11–50% of daily allowance

1.18

1.05–1.27

< 0.001

> 50% of daily allowance

1.37

1.10–1.64

< 0.001

Time in the day WPS(Ref: Always afternoon)

 Always morning

1.97

1.31–2.27

< 0.001

 Morning more than afternoon

1.47

1.27–1.69

< 0.001

 Afternoon more than morning

1.28

1.20–1.56

< 0.001

Waterpipe smoking father(Ref: No)

1.04

0.97–1.08

0.486

Waterpipe smoking mother(Ref: No)

1.03

0.98–1.07

0.216

Waterpipe smoking friends(Ref: No)

1.02

0.97–1.05

0.605

Normative beliefs

 Successful people smoke waterpipe (Ref: No)

1.16

0.99–1.23

0.052

 Cool people smoke waterpipe (Ref: No)

0.99

0.95–1.15

0.575

 My idols smoke waterpipe (Ref: No)

1.13

0.99–1.27

0.073

 My friends disapprove WPS (Ref: Yes)

1.25

1.17–1.34

0.019