A subset of the genotyped NTR sample (N = 5148) had declared never to have used cannabis, or declared an age at onset older than 10 years of age in survey 2009 (which included an open ended question on age at onset, see above). Among them, 852 (16.6 %) had initiated cannabis use, whereas 4296 observations had not initiated at the time of data collection (i.e., censored observations). The participants were clustered within 2992 families of sizes varying from 1 to 8 members. Females represented 62.3 % of the sample and the age ranged between 16 and 99 years (mean age = 46.93, SD = 17.54).
