. Author manuscript; available in PMC: 2010 Feb 17.

Published in final edited form as: JAMA. 2008 Feb 6;299(5):525–531. doi: 10.1001/jama.299.5.525

Table 3.

Tobacco Smoking by Weekly Cannabis Use at Ages 18 Through 32 Years

Cannabis Used at Least Weekly	Cumulative Tobacco Smoking to That Age, Mean (SD),Pack-Years	Median Tobacco Smoking to That Age, Pack-Years (Interquartile Range)
Age 18 years
No	0.51 (0.96)^a	0.00 (0.00–0.68)

Yes	2.21 (1.57)	2.25 (1.00–3.00)

Age 21 years
No	1.17 (1.91)^a	0.00 (0.00–1.90)

Yes	3.48 (2.68)	3.05 (1.20–5.50)

Age 26 years
No	2.43 (3.58)^a	0.00 (0.00–4.50)

Yes	6.34 (4.68)	6.75 (1.60–10.00)

Age 32 years
No	3.75 (5.60)^a	0.00 (0.00–6.85)

Yes	10.90 (7.37)	12.43 (4.83–16.06)

At any of ages 18, 21, 26, or 32 years
No	3.06 (5.04)^a	0.00 (0.00–4.93)

Yes	9.48 (7.31)	9.43 (2.84–15.18)

At each of ages 18, 21, 26, or 32 years
No	4.32 (5.99)^a	0.00 (0.00–7.95)

Yes	15.32 (6.37)	15.98 (13.46–19.81)

P < .001.