Table 1.
Overview of twin studies into lifetime cannabis use. Studies in bold are used in the present meta-analysis.
| Cohort | Reference | Country | Age | Measure | Prevalence (in %) | Sex | MZ (pairs) | DZ (pairs) | A (in %) | C (in %) | E (in %) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Agrawal et al., 2008a (29) | Australia | 24–36 | Use prior to age 17 | 60.2 (lifetime use) | M F OS |
494 698 |
395 513 661 |
72 (64–80) | - | 28 (20–36) |
| 1 | Agrawal et al., 2007 (47) | Australia | 24–36 | Experimentation | M: 69 F: 53 |
M F |
487 696 |
387 506 |
48 (46–50) 44 (41–49) |
22 (12–41) 28 (26–35) |
30 (28–31) 28 (20–29) |
| 1 | Lynskey et al., 2007 (70) | Australia | 24–36 | Lifetime use | Not reported | M/F | 6265 individuals | 60 (45–72) | 9 (1–22) | 32 (26–36) | |
| 1 | Lynskey et al., 2002 (33) | Australia | 24–36 | Lifetime use |
M: 68.8 F: 53.2 |
M F OS |
487 699 |
387 507 655 |
67 (9–75) 45 (18–70) |
0 (0–50) 26 (3–49) |
33 (25–43) 29 (23–37) |
| 2 | Agrawal et al., 2005 (49) | US, Virginia cohort 1 | M 20–58 F 21–62 |
Cannabis use | 48–53 | M F |
702 556 |
489 378 |
56 56 |
26 28 |
18 16 |
| 2 | Agrawal et al., 2004a (71) | US, Virginia cohort 1 | M 20–58 F 21–62 |
Early use, before age 18 | M: 52.9 F: 46.6 (lifetime use) |
M F |
1196 MM pairs 934 FF pairs |
16 40 |
52 38 |
32 22 |
|
| 2 | Agrawal et al., 2004b (72) | US, Virginia cohort 1 | M 20–58 F 21–62 |
Ever used | M: 54 F: 48 |
M F |
2953 individuals 2132 individuals |
36 (17–41) | 35 (16–39) | 29 (25–34) | |
| 2 | Agrawal et al., 2004c (57) | US, Virginia cohort 1 | M 20–58 F 21–62 |
Lifetime use | M: ~53 F: ~48 |
M F |
2632 individuals 1943 individuals |
23 46 |
45 29 |
32 25 |
|
| 2 | Agrawal et al., 2004d (53) | US, Virginia cohort 1 | M 20–58 F 21–62 |
Lifetime use | M: 54.0 F: 47.6 |
M F |
702 556 |
489 378 |
27 (9–54) 29 (7–55) |
42 (40–48) 50 (49–69) |
31 (30–36) 21 (17–26) |
| 2 | Gillespie et al., 2009 (50) | US, Virginia cohort 1 | 24–62 (at wave 3) | Initiation | 54 | M | 1772 individuals | 27 | 42 | 3 | |
| 2 | Karkowski et al., 2000 (73) | US, Virginia cohort 1 | M = 30.1 ± 7.6 | Lifetime use | Not reported | F | 499 | 327 | 59 (44–73) | 19 (9–31) | 21 |
| 2 | Kendler et al., 2005 (74) | US, Virginia cohort 1 | F: 36.6 ± 8.1 M/OS twins: 36.8 ± 9.1 |
Lifetime use | M: 39–63 F: 33–55 (differs per age group) |
M F |
880/1445/584 pairs 485/1149/283 pairs (wave 1/2/3) |
41 (19–63) | 29 (9–48) | 30 (25–36) | |
| 2 | Kendler et al., 2003 (54) | US, Virginia cohort 1 | 20–58 | Lifetime use | 54.0 | M | 704 | 492 | 35 | 35 | 30 |
| 2 | Kendler et al., 2000 (75) | US, Virginia cohort 1 | 20–58 | Lifetime use |
MZ: 50.4 DZ: 55.9 |
M | 708 | 490 | 33 (5–60) | 34 (10–58) | 33 (26–40) |
| 2 | Kendler et al., 1999 (76) | US, Virginia cohort 1 | 37.7 ± 7.5 | Lifetime use | 48.7 | F | 1934 individuals | 46 (18–77) | 29 (0–54) | 25 (20–32) | |
| 2 | Kendler et al., 1998 (77) | US, Virginia cohort 1 | 22–62 | Lifetime use |
MZ: 46.0 DZ: 52.8 |
F | 485 | 335 | 40 (10–72) | 35 (6–60) | 25 (18–34) |
| 2 | Neale et al., 2006 (78) | US, Virginia cohort 1 | Not reported | Lifetime use | Not reported | F | 499 | 327 | 48 | 28 | 25 |
| 3 | Maes et al., 1999 (28) | US, Virginia cohort 2 | 8–16 | Lifetime use |
M: 0.0–12.6 F: 0.0–10.9 (differs per age) |
M F OS |
300 389 |
184 187 295 |
22 (0–78) | 68 (15–93) | 9 (2–27) |
| 4 | Lessem et al., 2006 (79) | US, Add Health | Wave 1: M = 16.2 ± 1.7 Wave 2: M = 16.7 ± 1.6 |
Ever used | 35 | M/F | 4846/4413 (Pairs per wave, includes sibling pairs) | 21 (0–51) | 57 (32–76) | 22 (10–42) | |
| 4 | Miles et al., 2001 (80) | US, Add Health | 13–21 | Ever used | 35 |
M F OS |
144 145 |
131 114 204 |
31 (1–61) | 47 (21–69) | 22 (14–34) |
| 5 | McGue et al., 2000 (27) | US, Minnesota cohort 2 | 17 | Ever used |
M: 20.4 F: 24.0 |
M F |
188 223 |
101 114 |
26 13 |
56 61 |
18 26 |
| 6 | Rhee et al., 2003 (34) | US, Colorado | 12–19 | Initiation |
M: 27.2 F: 27.1 |
M F OS |
159 186 |
113 101 123 ** 306 siblings 74 adoptive |
39 (2–81) 72 (29–.95) |
44 (7–73) 24 (2–65) |
17 (7–34) 4 (1–12) |
| 7 | Fowler et al., 2007 (51) | UK | 11–19 | Initiation | 24 | M/F | 461 | 714 | 35 (5–63) | 47 (24–71) | 18 (10–36) |
| 7 | Shelton et al., 2007 (81) | UK |
Time 1: 5–13 Time 2: 11– 20 |
Initiation |
M: 22 F: 21 |
M F OS |
177 248 |
132 189 342 |
35 (5–63) | 47 (24–71) | 18 (10–36) |
| 8 | Grant et al., 2006 (68) | US, VETR | 36–55 | Ever used | ~40 | M | 1583 | 1255 | 60 | 8 | 32 |
| 8 | Tsuang et al., 1999 (82) | US, VETR | 36–55 | Transition from exposure to initiation | 47.2 (lifetime use) | M | 1874 | 1498 | 44 (22–60) | 10 (0–28) | 46 (39–53) |
| 9 | Vink et al. (submitted) (44) | the Netherlands | 21–40 | Cannabis initiation |
M: 36.2 F: 24.7 |
M F OS |
158 422 211 |
98 205 |
44 (16–74) | 31 (4–55) | 24 (17–33) |
A = additive genetic variance, C = shared environmental variance, E = unshared environmental variance