Table 2.

Negative binomial regression predicting adjusted usual quantity of marijuana use among purchasers (N=777)

	IRR1	95% CI	P
How high usually got:
Not at all high	1.00
A little high	0.76	(0.42, 1.35)	0.350
Moderately high	1.25	(0.72, 2.15)	0.430
Very high	2.09	(1.06, 4.11)	0.032
Frequency of use:
(Nearly) every day	0.45	(0.31, 0.65)	<0.001
About once a week	0.67	(0.45, 0.99)	0.046
Once every 2/3 weeks	0.87	(0.53, 1.46)	0.606
Once every month or 2	1.06	(0.69, 1.61)	0.800
Less often than that	1.00
Medical recommendation	1.24	(0.90, 1.70)	0.189
Type of use:
Smokable	1.00
Inhalable	1.16	(0.80, 1.68)	0.442
Edible	0.78	(0.53, 1.17)	0.232
Other	0.28	(0.13, 0.59)	0.001
Gender male	1.30	(1.05, 1.61)	0.014
Age :
18–29	1.00
30–39	1.34	(0.92, 1.94)	0.126
40–49	1.05	(0.77, 1.45)	0.751
50–64	0.95	(0.68, 1.32)	0.760
65+	0.84	(0.47, 1.53)	0.574
Race/ethnicity:
White	1.00
Black	1.23	(0.81, 1.88)	0.334
Hispanic	1.01	(0.69, 1.49)	0.962
Others	0.91	(0.64, 1.29)	0.600
Education:
HS grad or less	1.00
Some college	0.91	(0.69, 1.19)	0.481
College grad	0.92	(0.66, 1.29)	0.630
Graduate school	0.66	(0.44, 0.99)	0.043
Marital status:
Married	1.00
Separate/divorced	0.97	(0.69, 1.35)	0.834
Widowed	1.22	(0.71, 2.10)	0.471
Single	1.15	(0.86, 1.54)	0.355
Family income:
≤20,000	1.00
$20,001–$50,000	0.84	(0.62, 1.16)	0.290
$50,001–$80,000	1.03	(0.71, 1.50)	0.873
>$80,000	1.05	(0.72, 1.53)	0.788
Missing	1.26	(0.77, 2.08)	0.357

¹IRR = Incidence rate ratio