2. Illicit Drug Use

The National Survey on Drug Use and Health (NSDUH) obtains information on nine different categories of illicit drug use: marijuana, cocaine, heroin, hallucinogens, inhalants, and nonmedical use of prescription-type pain relievers, tranquilizers, stimulants, and sedatives. Estimates of illicit drug use reflect any of the nine categories listed above. In 2004-2005, an estimated 8.0 percent of the population aged 12 or older had used an illicit drug in the past month, and the estimated percentage was similar in 2003-2004 (8.1 percent) (Table C.1). Marijuana, the most commonly used illicit drug, was used by 6.0 percent of the population in 2004-2005 during the past month (Table B.3).

2.1 Illicit Drugs

Estimates of past month use of illicit drugs ranged from a low of 5.9 percent in Iowa to a high of 12.2 percent in Alaska for all persons aged 12 or older (Table B.1). See Section 1.2 for a discussion of the proper use of the prediction intervals [PIs]. Colorado, Oregon, Rhode Island, and Vermont were in the highest fifth for all persons aged 12 or older and for each of the age subgroups: 12 to 17, 18 to 25, and 26 or older (Figures 2.1 to 2.4).

Two States showed significant decreases from 2003-2004 to 2004-2005 (at the 5 percent level of significance) in the percentage of all persons aged 12 or older who used an illicit drug in the past month: New Mexico (from 11.3 to 8.9 percent) and North Dakota (from 7.5 to 6.2 percent) (Table C.1). At the national level, the use of illicit drugs among youths aged 12 to 17 declined from 10.9 percent in 2003-2004 to 10.3 percent in 2004-2005 (approximately a 1.2 percent change between 2003 and 2005).⁷ The Western region contributed significantly to the national decline in the percentage of youths who used illicit drugs in the past month. Five States showed significant decreases among youths: California (from 12.1 to 10.6 percent), Michigan (from 12.3 to 10.6 percent), New Mexico (from 16.2 to 13.0 percent), North Dakota (from 10.8 to 8.5 percent), and Washington (from 11.7 to 9.6 percent). Among the 12 significant changes that occurred across all four age groups between 2003-2004 and 2004-2005, 11 were decreases (Table C.1).

2.2 Marijuana

Because marijuana is the predominant drug among those using an illicit drug, States that had high prevalence rates for illicit drug use also had high prevalence rates for past month use of marijuana. Eight out of ten States in the top fifth for past month use of an illicit drug among persons aged 12 or older also were ranked in the top fifth for past month use of marijuana. Seven States were common to the top fifth for past month marijuana use in all three age groups: 12 to 17, 18 to 25, and 26 or older: Alaska, Connecticut, Maine, Montana, Oregon, Rhode Island, and Vermont (Figures 2.1 and 2.9 to 2.12). Iowa had the lowest rate of past month use of marijuana (4.2 percent) in the 12 or older population, and Alaska had the highest rate (10.1 percent) (Table B.3).

Nationally in 2004-2005, 10.5 percent of all persons aged 12 or older reported marijuana use in the past year (Table B.2). Young adults, aged 18 to 25, reported the highest rate of past year use of marijuana, 27.9 percent. The State rankings for past year use were fairly similar to those for past month use of marijuana among persons 12 or older (Figures 2.5 and 2.9). Iowa had the lowest rate (8.0 percent) of past year use of marijuana among persons aged 12 or older. Alaska had the highest rate of past year marijuana use in that age group (16.0 percent). Rhode Island had the highest rate of past year marijuana use in the Nation in the 18 to 25 age group (42.1 percent).

Six States showed significant decreases in the past year use of marijuana among all persons aged 12 or older between 2003-2004 and 2004-2005: Iowa (from 9.4 to 8.0 percent), Massachusetts (from 14.2 to 12.5 percent), Missouri (from 11.9 to 10.6 percent), New Hampshire (from 14.6 to 12.6 percent), New Mexico (from 13.3 to 11.0 percent), and North Dakota (from 10.1 to 8.5 percent) (Table C.2). Only one State, Tennessee, showed a significant increase among persons aged 12 or older, from 8.4 to 10.3 percent. Three States that showed significant decreases from 2003-2004 to 2004-2005 in past year marijuana use for the 12 or older age group also displayed decreases in past month marijuana use (Massachusetts, New Mexico, and North Dakota) (Table s C.2 and C.3). Nationally, there was a significant decrease in the past month use of marijuana among youths aged 12 to 17 (from 7.7 to 7.2 percent), and past year use of marijuana among youths also decreased from 14.7 to 13.9 percent over the same period (Table s C.2 and C.3).

2.3 Perceptions of Risk of Marijuana Use

An individual's perception of the risks of substance use has been shown to be inversely related to whether he or she actually uses the substance (e.g., Bachman, Johnston, & O'Malley, 1998). At the State level, 7 of the 10 States that ranked in the lowest fifth of perceived great risk of using marijuana once a month were also among the States ranked in the highest fifth for past month use of marijuana in 2004-2005 for persons aged 12 or older (Figures 2.9 and 2.13).

Slightly over one quarter (27.1 percent) of all persons aged 12 or older in New Hampshire reported that using marijuana occasionally (once a month) was a great risk (Table B.4). However, in Mississippi slightly more than half (51.2 percent) of all persons aged 12 or older indicated that occasional use of marijuana was a great risk. Although Mississippi (4.8 percent) did not have the lowest rate for past month use of marijuana among persons aged 12 or older, it ranked in the lowest fifth for that measure (Table B.3 and Figure 2.9).

The national percentage of persons aged 12 or older perceiving a great risk of using marijuana once a month decreased significantly between 2003-2004 and 2004-2005, from 39.7 to 39.0 percent (Table C.4). Although there was a decline in perceived risk in the general population, there were no increases in past month use of marijuana for any State in any age group (Table C.3) . Four States played a role in contributing to the national decrease in perceived risk: Kansas (from 43.5 to 39.8 percent), Louisiana (from 45.7 to 42.4 percent), Montana (from 39.0 to 36.0 percent), and Oregon (from 33.2 to 30.1 percent) (Table C.4). No State showed a significant increase in any of the age groups in the perceived great risk of using marijuana once a month.

2.4 Incidence of Marijuana Use

Related to the prevalence of marijuana use is the number of persons in a period of time who used marijuana for the first time ever. When the number of first-time users of a substance increases for a number of consecutive years, the prevalence rate for the substance tends to increase also. The average annual incidence of marijuana for this report is estimated somewhat differently than in the national report (OAS, 2006b).⁸ The estimate for a single year is averaged over the 2 most recent years and expressed as a rate per 100 person years of exposure. For the combined years 2004-2005, the national marijuana incidence rate for all persons aged 12 or older was 1.7 percent (Table B.5). Alaska had the highest rate, 2.6 percent. Alabama, Arkansas, Florida, Mississippi, and West Virginia shared the lowest rate, 1.4 percent.

Eight States that were ranked in the top fifth for marijuana incidence in the 12 or older age group also ranked in the top fifth for past month marijuana use (Alaska, Colorado, Connecticut, Montana, New Hampshire, Oregon, Rhode Island, and Vermont) (Figures 2.9 and 2.17). Because most initiation of marijuana takes place at age 25 or earlier (Gfroerer, Wu, & Penne, 2002), the rates of initiation in the 26 or older age group were much lower than those in the 18 to 25 and 12 to 17 age groups: The national rates were 0.2, 6.2, and 5.8 percent, respectively (Table B.5). Connecticut had the highest rate among youths aged 12 to 17 (8.0 percent), and New Hampshire had the highest rate among persons aged 18 to 25 (10.1 percent).

Rates of first use of marijuana declined significantly among youths between 2003-2004 and 2004-2005 (from 6.3 to 5.8 percent), young adults aged 18 to 25 (from 6.6 to 6.2 percent), and in the overall population aged 12 or older (from 1.8 to 1.7 percent) (Table C.5). Five States showed significant decreases in marijuana incidence among persons 12 or older. The only significant increase in marijuana incidence was in the 26 or older age group for Hawaii (increased from 0.1 percent in 2003-2004 to 0.2 percent in 2004-2005).

2.5 Illicit Drugs Other Than Marijuana

Illicit drugs other than marijuana include cocaine, heroin, hallucinogens, inhalants, and the nonmedical use of prescription-type pain relievers, tranquilizers, stimulants, and sedatives. The national estimate of past month use of illicit drugs other than marijuana among persons aged 12 or older was 3.6 percent for 2004-2005 combined (Table B.6). North Dakota and South Dakota had the lowest rate (2.8 percent) of past month use of an illicit drug other than marijuana among persons 12 or older, and Colorado had the highest rate (4.5 percent). Three States that were in the top fifth for past month use of an illicit drug among those aged 12 or older also were ranked in the top fifth for past month use of an illicit drug other than marijuana: Alaska, Colorado, and Rhode Island (Figures 2.1 and 2.20).

Past month use of illicit drugs other than marijuana was relatively stable between 2003-2004 and 2004-2005 among all persons aged 12 or older; however, among youths aged 12 to 17, the rates dropped from 5.5 to 5.1 percent (Table C.6). The rate of past month use of illicit drugs other than marijuana in Texas changed from 5.8 to 4.7 percent and shared in the national decrease among youths. Among persons aged 18 to 25, two States showed significant increases: Connecticut (from 8.7 to 11.4 percent) and Tennessee (from 7.4 to 9.8 percent).

2.6 Cocaine

The 2004-2005 national prevalence rate for the use of cocaine in the past year among all persons aged 12 or older was 2.3 percent (Table B.7). Because cocaine is one of the substances included in the "illicit drug use other than marijuana" category, it is useful to compare the rankings of States with respect to these two measures. In 2004-2005, only three States (Alaska, Colorado, and Rhode Island) ranked in the highest fifth for both past month use of an illicit drug other than marijuana (aged 12 or older) and past year use of cocaine (aged 12 or older) (Figures 2.20 and 2.24). The District of Columbia had the highest rate of past year cocaine use (3.4 percent) among persons aged 12 or older; North Dakota had the lowest rate (1.7 percent) in that population (Table B.7). Massachusetts was the only State that ranked in the top fifth for past year cocaine use among all three age groups (12 to 17, 18 to 25, and 26 or older) (Figures 2.25 to 2.27).

California (from 2.6 to 2.2 percent) and New Mexico (from 3.1 to 2.3 percent) showed significant decreases in past year cocaine use among persons aged 12 or older between 2003-2004 and 2004-2005 (Table C.7). The District of Columbia showed an increase in past year cocaine use among young adults aged 18 to 25, from 4.1 to 5.8 percent.

2.7 Pain Relievers (Nonmedical Use)

In 2004-2005, 4.8 percent of all persons aged 12 or older reported having used pain relievers nonmedically in the past year, a percentage that was unchanged from 2003-2004 (Table B.8). Utah had the highest percentage (6.5 percent) of persons aged 12 or older using pain relievers for nonmedical purposes in the past year. South Dakota had the lowest rate in the Nation—3.4 percent. Kentucky and Oklahoma ranked in the top fifth of States for this measure in each of the three age groups and for the total population aged 12 or older (Figures 2.28 to 2.31).

Although the nonmedical use of pain relievers among the general population aged 12 or older remained unchanged between 2003-2004 and 2004-2005, a significant decrease occurred among youths aged 12 to 17 (from 7.5 to 7.1 percent) (Table C.8). Among all persons 12 or older, Georgia showed a decline in the prevalence rate, from 5.5 percent in 2003-2004 to 4.3 percent in 2004-2005. Tennessee, on the other hand, showed an increase from 4.6 to 5.5 percent.