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Table 3 Multivariable models examining the association of substance use perception, presence of close friends with alcohol or drug problems, and family history of alcohol or drug problems with substance use

From: Perception of tobacco, cannabis, and alcohol use of others is associated with one’s own use

Model 1: tobacco use* Cigarettes/week, IRR (95% CI)
Perception of tobacco use of others (same age/sex), reference group = accurate estimation of tobacco use of others  
Overestimation of tobacco use by others 1.17 (1.05; 1.32)
Underestimation of tobacco use by others 0.99 (0.84; 1.17)
Close friends with alcohol or drug problems 2.08 (1.83; 2.35)
Family history of alcohol problems (parents/siblings) 1.48 (1.25; 1.75)
Family history of drug problems (parents/siblings) 1.52 (1.22; 1.89)
Model 2: cannabis use* Days of cannabis use/month, IRR (95% CI)
Perception of cannabis use of others (same age/sex), reference group = accurate estimation of cannabis use of others  
Overestimation of cannabis use by others 1.43 (1.21; 1.70)
Underestimation of cannabis use by others 0.62 (0.23; 0.75)
Close friends with alcohol or drug problems 2.91 (2.48; 3.42)
Family history of alcohol problems (parents/siblings) 1.12 (0.89; 1.42)
Family history of drug problems (parents/siblings) 1.78 (1.36; 2.33)
Model 3: drinking* Drinks/week, IRR (95% CI)
Perception of drinking of others (same age/sex), reference group = accurate estimation of drinking of others  
Overestimation of drinking of others 1.57 (1.43; 1.72)
Underestimation of drinking of others 0.41 (0.34; 0.50)
Close friends with alcohol or drug problems 1.43 (1.28; 1.59)
Family history of alcohol problems (parents/siblings) 1.35 (1.17; 1.55)
Family history of drug problems (parents/siblings) 1.38 (1.14; 1.67)
  1. *All models were adjusted for age, education level, and linguistic region. IRR = incidence rate ratio.