Initiation of Marijuana Use: Trends, Patterns, and Implications

4. State Incidence Estimates

4.1 Introduction

This chapter summarizes estimates of recent marijuana initiation (new use in the past 24 months) for the 50 States and the District of Columbia based on the combined data from the 1999 and 2000 National Household Surveys on Drug Abuse (NHSDAs). These estimates were derived from a model that used a large number of variables and data collected from each State and the District of Columbia. Note that State-level incidence estimates reported in this chapter are different from those of the other chapters. That is, the State-level estimates in this chapter are referred to as the average annual marijuana initiates over the past 24 months prior to the NHSDA interview. They are presented by the following age groupings: 12 to 17 years, 18 to 25 years, 26 years or older, and a combined total for all ages 12 or older. For more information about the methodology used to generate State-level estimates of substance use, refer to State Estimates of Substance Use from the 2000 NHSDA (Wright, in press).

4.2 State-Level Estimates of Recent New Marijuana Users

Table 4.1 displays estimated numbers of the average annual marijuana initiates over the past 24 months by age group and State. Also included in the table are their corresponding 95 percent prediction intervals that indicate the precision of the estimates. The prediction interval reflects the uncertainty associated with sampling variability and model bias. There is a 95 percent probability that the true value lies within the interval.

Overall, the combined 1999 and 2000 NHSDAs estimated that there were approximately 2.3 million recent new marijuana users annually. On average, there were an estimated 1.2 million recent marijuana initiates aged 12 to 17 annually, 0.9 million recent initiates aged 18 to 25 , and 0.1 million recent initiates aged 26 or older. These averaged annual numbers of recent new marijuana users varied by States.

Estimated average annual rates of first use of marijuana over the past 24 months and associated 95 percent prediction intervals, by age group and State, are summarized in Table 4.2. Among all persons aged 12 or older, there were an estimated 1.5 marijuana initiates per 1,000 potential new users annually. The average annual incidence rate was about the same for youths aged 12 to 17 (6.1) and young adults aged 18 to 25 (5.5), while it was very low (0.1) among adults aged 26 or older.

The average annual incidence rates varied slightly across different individual States, and the pattern of distributions also differed by age group. This chapter's figures (maps) display the ranking of these incidence rates by State for all respondents aged 12 or older and for two young age groups (ages 12 to 17 and ages 18 to 25). The color of each State on the maps indicates how the State ranks relative to other States. States can fall into one of five groups according to their ranking. Those States with the highest incidence rate are colored red; those with the lowest estimates are white. Approximately 10 States are included in each group. In some cases, a group may contain more or fewer than 10 States because the estimate is the same for 2 or more States in that group. It should be noted that some prediction intervals around State-level estimates are fairly sizable, which means that some estimates that appear to be different from each other may not be statistically significant. In particular, States with lower rates of recent first use tend to have wider confidence intervals than those with higher rates.

The 10 States with the highest overall rates of recent new marijuana users were as follows (Figure 4.1):

The 10 States with the lowest overall rates of recent new marijuana users were Alabama, Arkansas, Florida, Indiana, Louisiana, New Jersey, New York, Pennsylvania, Virginia, and West Virginia.

The nine States with the highest rates of recent new marijuana users aged 12 to 17 were as follows (Figure 4.2):

The 10 States with the lowest rates of recent marijuana initiates aged 12 to 17 were Alabama, District of Columbia, Idaho, Louisiana, Mississippi, New Jersey, Pennsylvania, Texas, Utah, and Virginia.

Figure 4.1 Average Annual Incidence of Marijuana Use among Persons Aged 12 or Older: 1999 and 2000

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

Figure 4.2 Average Annual Incidence of Marijuana Use among Youths Aged 12 to 17: 1999 and 2000

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

The 10 States with the highest incidence rates among adults aged 18 to 25 were as follows (Figure 4.3):

The 10 States with the lowest incidence rates among adults aged 18 to 25 were Arizona, Arkansas, California, Florida, Louisiana, Oklahoma, South Carolina, Texas, Utah, and West Virginia.

Because of a very low rate of recent marijuana initiation among adults aged 26 or older, the distribution of State-level estimates is not shown in a figure.

Figure 4.3 Average Annual Incidence of Marijuana Use among Young Adults Aged 18 to 25: 1999 and 2000

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

These average annual incidence rates varied slightly across different States and age groups. Across different age groups, only a few States were consistently found to be in the highest or lowest category of recent initiation. Colorado, Delaware, Massachusetts, New Hampshire, and Vermont were ranked in the top 10 for the overall age group, the youth age group, and the young adult age group. New Mexico had the highest rate for the overall and youth age groups. Minnesota had the highest rate for the overall and young adult age groups. By comparison, Louisiana had the lowest rate of recent new users for the overall, youth, and young adult age groups. In addition, Texas and Utah had the lowest rates of recent initiation among youths and young adults.

Table 4.1 Estimated Numbers (in Thousands) of Average Annual Marijuana Initiates, by Age Group and State: 1999 and 2000
State	Total					Age Group (Years)
						12-17					18-25					26 or Older
	Estimate	Prediction Interval				Estimate	Prediction Interval				Estimate	Prediction Interval				Estimate	Prediction Interval
Total	2,268					1,230					898					139
Alabama	34	(29	-	39)		17	(13	-	21)		15	(12	-	19)		2	(1	-	4)
Alaska	6	(5	-	7)		4	(3	-	4)		2	(2	-	3)		0	(0	-	1)
Arizona	45	(39	-	52)		29	(24	-	35)		13	(10	-	17)		2	(1	-	4)
Arkansas	21	(18	-	24)		11	(9	-	14)		8	(6	-	10)		1	(1	-	2)
California	246	(226	-	267)		135	(123	-	148)		93	(79	-	109)		17	(11	-	26)
Colorado	38	(32	-	44)		22	(18	-	27)		14	(10	-	18)		2	(1	-	4)
Connecticut	26	(22	-	30)		15	(12	-	18)		10	(7	-	12)		2	(1	-	3)
Delaware	7	(6	-	8)		4	(4	-	5)		3	(2	-	3)		0	(0	-	1)
District of Columbia	4	(4	-	5)		2	(2	-	3)		2	(1	-	2)		0	(0	-	1)
Florida	105	(95	-	115)		59	(53	-	67)		38	(32	-	44)		7	(4	-	12)
Georgia	65	(56	-	74)		33	(28	-	39)		28	(22	-	35)		4	(2	-	7)
Hawaii	10	(8	-	11)		6	(5	-	7)		3	(2	-	4)		0	(0	-	1)
Idaho	11	(10	-	13)		6	(5	-	7)		5	(4	-	7)		1	(0	-	1)
Illinois	99	(90	-	108)		53	(47	-	60)		40	(34	-	46)		6	(4	-	9)
Indiana	49	(42	-	56)		26	(22	-	32)		19	(15	-	24)		3	(2	-	5)
Iowa	26	(22	-	29)		14	(11	-	17)		10	(8	-	13)		1	(1	-	3)
Kansas	25	(22	-	29)		13	(11	-	16)		11	(9	-	14)		1	(1	-	2)
Kentucky	37	(32	-	42)		19	(16	-	23)		16	(13	-	19)		2	(1	-	4)
Louisiana	36	(31	-	42)		20	(17	-	25)		13	(10	-	17)		2	(1	-	4)
Maine	11	(10	-	13)		6	(5	-	7)		4	(3	-	6)		1	(0	-	1)
Maryland	42	(36	-	48)		21	(17	-	26)		18	(14	-	22)		3	(1	-	4)
Massachusetts	60	(51	-	68)		36	(30	-	43)		20	(15	-	26)		3	(2	-	6)
Michigan	92	(84	-	101)		51	(46	-	57)		36	(31	-	42)		5	(3	-	8)
Minnesota	48	(42	-	55)		24	(20	-	28)		22	(18	-	27)		2	(1	-	4)
Mississippi	25	(21	-	29)		12	(10	-	15)		11	(9	-	14)		1	(1	-	3)
Missouri	46	(40	-	53)		25	(20	-	30)		19	(15	-	24)		3	(1	-	4)
Montana	9	(8	-	10)		5	(4	-	6)		3	(3	-	4)		0	(0	-	1)
Nebraska	15	(13	-	17)		8	(6	-	10)		6	(5	-	8)		1	(0	-	1)
Nevada	15	(13	-	17)		9	(7	-	11)		5	(4	-	6)		1	(0	-	2)
New Hampshire	11	(10	-	13)		7	(5	-	8)		4	(3	-	5)		1	(0	-	1)
New Jersey	64	(55	-	74)		31	(25	-	37)		29	(22	-	37)		5	(2	-	8)
New Mexico	18	(15	-	21)		11	(9	-	13)		6	(5	-	8)		1	(0	-	2)
New York	144	(130	-	159)		73	(65	-	83)		62	(52	-	72)		9	(6	-	14)
North Carolina	65	(56	-	74)		38	(32	-	44)		23	(18	-	29)		4	(2	-	7)
North Dakota	7	(6	-	8)		4	(3	-	5)		3	(2	-	4)		0	(0	-	1)
Ohio	94	(85	-	102)		50	(44	-	56)		39	(33	-	45)		5	(3	-	8)
Oklahoma	28	(24	-	33)		17	(14	-	21)		9	(7	-	12)		2	(1	-	3)
Oregon	28	(24	-	33)		15	(12	-	18)		12	(9	-	15)		2	(1	-	3)
Pennsylvania	92	(83	-	101)		46	(41	-	52)		40	(34	-	46)		6	(3	-	9)
Rhode Island	9	(8	-	10)		5	(4	-	6)		3	(2	-	4)		1	(0	-	1)
South Carolina	32	(27	-	37)		18	(15	-	22)		12	(9	-	15)		2	(1	-	4)
South Dakota	7	(6	-	8)		4	(3	-	5)		3	(2	-	4)		0	(0	-	1)
Tennessee	47	(40	-	54)		26	(21	-	31)		19	(14	-	24)		3	(2	-	5)
Texas	168	(153	-	184)		90	(81	-	101)		67	(58	-	78)		10	(6	-	16)
Utah	20	(17	-	24)		10	(8	-	13)		9	(7	-	11)		1	(1	-	2)
Vermont	6	(5	-	7)		4	(3	-	4)		2	(2	-	3)		0	(0	-	1)
Virginia	53	(45	-	61)		26	(21	-	31)		23	(18	-	30)		4	(2	-	7)
Washington	49	(43	-	57)		28	(23	-	33)		18	(14	-	23)		3	(2	-	5)
West Virginia	14	(12	-	17)		8	(6	-	9)		6	(5	-	7)		1	(0	-	2)
Wisconsin	53	(46	-	60)		30	(26	-	35)		20	(16	-	25)		3	(1	-	6)
Wyoming	5	(4	-	6)		3	(2	-	3)		2	(2	-	2)		0	(0	-	0)
Note: Estimates are based on a survey-weighted hierarchical Bayes estimation approach, and the 95 percent prediction (credible) intervals are generated by Markov Chain Monte Carlo techniques. Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

 

Table 4.2 Average Annual Rates of First Use of Marijuana, by Age Group and State: 1999 and 2000
State	Total					Age Group (Years)
						12-17					18-25					26 or Older
	Estimate	Prediction Interval				Estimate	Prediction Interval				Estimate	Prediction Interval				Estimate	Prediction Interval
Total	1.52					6.08					5.47					0.12
Alabama	1.28	(1.08	-	1.51)		5.19	(4.09	-	6.56)		5.35	(4.18	-	6.81)		0.10	(0.06	-	0.20)
Alaska	2.32	(1.96	-	2.74)		7.29	(5.96	-	8.89)		6.48	(4.95	-	8.46)		0.17	(0.09	-	0.32)
Arizona	1.82	(1.54	-	2.15)		8.16	(6.69	-	9.92)		4.69	(3.53	-	6.19)		0.13	(0.07	-	0.25)
Arkansas	1.32	(1.12	-	1.55)		5.75	(4.65	-	7.09)		4.58	(3.58	-	5.84)		0.10	(0.06	-	0.19)
California	1.46	(1.33	-	1.61)		5.57	(5.05	-	6.15)		4.50	(3.83	-	5.29)		0.14	(0.09	-	0.22)
Colorado	2.01	(1.69	-	2.40)		7.68	(6.19	-	9.47)		7.03	(5.34	-	9.20)		0.15	(0.08	-	0.29)
Connecticut	1.59	(1.32	-	1.92)		6.83	(5.45	-	8.53)		6.47	(4.84	-	8.60)		0.13	(0.07	-	0.25)
Delaware	1.90	(1.61	-	2.24)		8.32	(6.83	-	10.10)		7.01	(5.33	-	9.17)		0.13	(0.07	-	0.25)
District of Columbia	1.48	(1.24	-	1.77)		5.54	(4.34	-	7.05)		5.28	(4.06	-	6.83)		0.13	(0.07	-	0.26)
Florida	1.21	(1.09	-	1.34)		5.76	(5.06	-	6.55)		4.67	(3.96	-	5.50)		0.11	(0.06	-	0.18)
Georgia	1.50	(1.28	-	1.76)		5.61	(4.67	-	6.71)		5.47	(4.25	-	7.00)		0.13	(0.07	-	0.23)
Hawaii	1.65	(1.38	-	1.97)		7.63	(6.16	-	9.41)		5.50	(4.01	-	7.50)		0.11	(0.04	-	0.26)
Idaho	1.58	(1.33	-	1.87)		4.91	(3.93	-	6.11)		5.39	(4.20	-	6.88)		0.13	(0.07	-	0.24)
Illinois	1.56	(1.41	-	1.73)		6.17	(5.45	-	6.97)		5.61	(4.80	-	6.55)		0.12	(0.08	-	0.20)
Indiana	1.44	(1.23	-	1.69)		5.88	(4.82	-	7.15)		5.27	(4.1