Table 1.

Sample Size, Number of Observations, and Prevalence of Cannabis Use and Legalization by Study

	Age (years)
Study	13	14	15	16	17	18	Total
Observations (k)
TIP (n=283)	124	105	114	101	107	89	640
RIGS (n=471)	427	442	441	427	407	392	2,536
3GS (n=186)	81	97	67	102	36	91	474
Total (N=940)	632	644	622	630	550	572	3,650
Prevalence past-year cannabis use
TIP	0%	7%	10%	16%	27%	38%	15%
RIGS	3%	5%	8%	15%	20%	29%	13%
3GS	10%	8%	34%	31%	33%	40%	25%
Total	3%	6%	11%	17%	22%	32%	15%
Frequency past-year cannabis use
TIP
No use	100%	93%	90%	84%	73%	62%	85%
1 −20 times	0%	7%	8%	13%	18%	56%	11%
≥21 times	0%	0%	2%	3%	9%	12%	4%
RIGS
No use	97%	95%	92%	85%	80%	71%	87%
1 −20 times	2%	4%	7%	11%	14%	20%	10%
≥21 times	<1%	1%	2%	4%	6%	9%	3%
3GS
No use	90%	92%	66%	69%	67%	60%	75%
1–20 times	6%	6%	24%	23%	25%	20%	16%
≥21 times	4%	2%	10%	9%	8%	20%	9%
Mean years in legal state (range 0–3)
TIP	0.80	0.91	0.97	1.06	0.95	0.88	0.93
RIGS	0.01	0.01	0.01	0.01	0.01	0.00	0.01
3GS	0.81	0.54	0.76	0.64	0.44	0.63	0.65
Total	0.25	0.23	0.26	0.28	0.22	0.24	0.26

Note: Percentages may sum to more than 100 due to rounding.

TIP, Seattle Social Development Project – The Intergenerational Project; RIGS, Rochester InterGenerational Study; 3GS, Three Generation Study.