Table 1.
Characteristics of 1812 offspring of Vietnam Era Twins, stratified by their cannabis and tobacco use behaviors.
| Covariate | Neither Tobacco nor Cannabis (N=558) | Cigarettes only (N=398) | Cannabis only (N=55) | Both (N=801) | |
|---|---|---|---|---|---|
| Tobacco 1st (N=583) | Cannabis 1st (N=79) | ||||
| Socio-demographic | |||||
| Age at interview < 21 years | 69.7 | 46.7 | 52.7 | 39.3 | 36.7 |
| Born after 1981 | 62.3 | 33.2 | 36.4 | 25.6 | 24.1 |
| Sex (Male) | 45.9 | 48.0 | 58.2 | 51.3 | 62.0 |
| Caucasian | 91.9 | 92.7 | 89.1 | 93.3 | 96.2 |
| Peers and parenting | |||||
| Current Peer smoking (yes/no) | 27.0 | 54.7 | 49.1 | 80.4 | 69.2 |
| Current Peer drug use (yes/no) | 34.4 | 57.4 | 85.5 | 93.3 | 84.6 |
| Parents were strict when child | 52.0 | 62.1 | 61.8 | 53.7 | 59.5 |
| Smoking related covariates # | |||||
| Age at 1st cigarette < 13 years | - | 20.1 | - | 34.3 | 2.5 |
| DSM-IV Nicotine dependence | - | 6.5 | - | 24.7 | 13.9 |
| Current smoker (in past 12 months) | - | 78.2 | - | 84.8 | 88.6 |
| Maximum cigarettes in 24 hours (40 or more) | - | 6.3 | - | 23.7 | 13.9 |
| Cigarettes per day (40 or more) | - | 2.8 | - | 12.0 | 7.8 |
| Quit for 2 or more weeks (3 or more times) | - | 37.6 | - | 41.6 | 47.1 |
| Cannabis related covariates # | |||||
| Age at 1st cannabis use < 15 years | - | - | 14.6 | 22.1 | 43.0 |
| DSM-IV cannabis abuse/dependence | - | - | 12.7 | 33.3 | 33.0 |
| Current cannabis use (in past 12 months) | - | - | 43.4 | 44.2 | 49.3 |
| Used cannabis 40+ times lifetime | - | - | 10.9 | 38.1 | 39.2 |
| Other psychopathology | |||||
| Other illicit drug use | 2.7 | 4.5 | 36.4 | 58.8 | 63.3 |
| DSM-IV conduct problems | 3.1 | 6.5 | 23.6 | 27.3 | 31.7 |
| DSM-IV ADHD (maternal report) | 11.1 | 16.1 | 15.6 | 18.8 | 17.5 |
| DSM-IV major depressive disorder | 9.1 | 11.3 | 18.2 | 23.5 | 21.5 |
| DSM-IV Generalized anxiety disorder | 1.8 | 5.3 | 9.1 | 7.9 | 3.8 |
| DSM-IV alcohol abuse/dependence | 2.9 | 21.7 | 32.7 | 55.3 | 45.6 |
| Ever got drunk | 22.8 | 66.1 | 74.6 | 93.7 | 89.9 |
| Weekly drunkenness | 1.1 | 12.3 | 20.0 | 32.9 | 29.1 |
| DSM-IV panic disorder | 6.0 | 8.3 | 10.9 | 14.6 | 15.2 |
| DSM-IV social phobia | 26.7 | 30.2 | 23.6 | 34.1 | 32.9 |
| Familial Vulnerability to Nicotine Dependence | |||||
| High genetic & High environmental risk | 71.8 | 68.0 | 73.3 | 65.3 | 81.0 |
| High genetic & Low environmental risk | 24.9 | 21.6 | 29.4 | 22.1 | 40.0 |
| Intermediate genetic & high environmental risk | 29.4 | 28.1 | 29.4 | 25.6 | 40.0 |
| Familial Vulnerability to Drug Dependence | |||||
| High genetic & High environmental risk | 24.3 | 24.5 | 30.4 | 18.9 | 17.9 |
| High genetic & Low environmental risk | 10.5 | 10.4 | 18.0 | 6.2 | 11.3 |
| Intermediate genetic & high environmental risk | 7.3 | 8.2 | 5.9 | 6.6 | 8.3 |