Table 4. Discrete-time survival analysis (DTSA) assessing initiation of cannabis use, based on prior use* of each substance, and assessing initiation of each substance, based on prior cannabis use*, adjusting for sociodemographic, state non-medical cannabis laws, and psychosocial variables, among 5-18 years old and 19-34 years old, separately.
| Prior use* of each substance in relation to initiating cannabis use | ||||||||
|---|---|---|---|---|---|---|---|---|
| Age-period | Cigarettes | E-cigarettes | Cigars | Alcohol | ||||
| aHR (95% CI) | p | aHR (95% CI) | p | aHR (95% CI) | p | aHR (95% CI) | p | |
| 5-18 years old | 5.41 (4.69-6.25) | <.001 | 3.33 (2.61-4.25) | <.001 | 6.22 (4.73-8.17) | <.001 | 3.79 (3.39-4.25) | <.001 |
| 19-34 years old | 2.40 (2.03-2.84) | <.001 | 1.67 (1.36-2.05) | <.001 | 2.11 (1.68-2.64) | <.001 | 2.51 (2.14-2.93) | <.001 |
| Prior use* of cannabis in relation to initiating use of each substance | ||||||||
| Age-period | Cigarettes | E-cigarettes | Cigars | Alcohol | ||||
| aHR (95% CI) | p | aHR (95% CI) | p | aHR (95% CI) | p | aHR (95% CI) | p | |
| 5-18 years old | 4.10 (3.54-4.75) | <.001 | 4.08 (3.45-4.82) | <.001 | 4.30 (3.64-5.07) | <.001 | 4.50 (3.91-5.19) | <.001 |
| 19-34 years old | 2.37 (1.95-2.88) | <.001 | 3.60 (3.11-4.17) | <.001 | 2.33 (1.91-2.84) | <.001 | 1.51 (1.24-1.83) | <.001 |
Notes: * Prior use defined as ever having used the substance by the age-period one year earlier (time-lagged predictor). Cigarette, e-cigarette, cigar, and alcohol use by the prior age-period (t–1) in relation to cannabis initiation in a specific age-period (t): LRTs on PH assumption across all time periods: LR=137.05, df=24, p<.001; LR=33.70, df=24, p=.014; LR=68.44, df=21, p<.001; LR=47.96, df=21, p<.001. LRTs on PH assumption across the 2 age-period categories (>18 vs. 5-18): cigarette, e-cigarette, cigar, and alcohol use by the prior age-period (t–1) in relation to cannabis initiation in a specific age-period (t): LR=76.05, df=1, p<.001; LR=17.26, df=1, p<.001; LR=57.78, df=21, p<.001; LR=9.53, df=21, p=.002. Cannabis use by the prior age-period (t–1) in relation to initiating cigarette, e-cigarette, cigar and alcohol use in a specific age-period (t): LRTs on PH assumption across all the time periods: LR=92.73, df=21, p<.001; LR=184.37, df=22, p<.001; LR=126.52, df=21, p<.001; LR=151.14, df=20, p<.001. LRTs on PH assumption across the 2 age-period categories (>18 vs. 5-18): cigarette, e-cigarette, cigar, and alcohol use by prior age-period (t–1) in relation to cannabis initiation in a specific age-period (t): LR=19.84, df=1, p<.001; LR=0.70, df=1, p=.404; LR=30.31, df=1, p<.001; LR=90.40, df=1, p<.001. Covariates in each model included: age, sex, sexual orientation, race, ethnicity, parental education, rurality, state non-medical cannabis laws, lifetime mental health diagnosis including depressive disorder, anxiety disorder, and ADD, and personality characteristics including extraversion, agreeableness, conscientiousness, emotional stability, and openness to new experiences (not shown in table).