Table I.

Lifetime use of alcohol and marijuana by gender, tribe and age.

	Males		Females
	Northern plains	Southwest	Northern plains	Southwest
	Number	Number	Number	Number
Age
<30 years	262	167	310	252
30–39 years	214	152	198	188
40+ years	226	218	248	304
All ages	702	537	756	744

	%	CI	%	CI	%	CI	%	CI
Lifetime use alcohol
<30 years	74.2	66.3–80.8sf	58.8	48.7–68.2sf,t	60.4	52.8–67.6sf	38.8	31.2–47.1nm,sm,nf
30–39 years	70.9	61.6–78.6sf	63.9	58.9–78.0sf,t	73.0	63.7–80.7sf	38.7	30.0–48.2nm,sm,nf
40+ years	79.5	70.6–86.2sf	75.5	67.1–82.4sf,t	69.2	60.8–76.6sf	38.5	31.2–46.3nm,sm,nf
All ages	74.6	69.7–78.9sf	68.1	62.6–73.2sf	67.1	62.3–71.5sf	38.7	34.0–43.5nm,sm,nf
Lifetime use marijuana
<30 years	46.6	38.4–55.lsf	44.8	35.2–54.9t	36.5	29.4–44.3t	29.5	22.7–37.5nm,t
30–39 years	42.3	33.5–51.7sf	39.0	29.3–50.0sf,t	38.7	29.8–48.4sf,t	16.8	10.9–25.0nm,sm,nf,t
40+ years	40.6	32.0–49.8sf	25.8	18.6–34.9sf,t	24.9	18.0–33.3sf,t	7.8	4.4–13.5nm,sm,nf,t
All ages	43.3	38.2–48.5sf	36.2	30.9–41.8sf	33.6	29.0–38.6sf	18.0	14.6–22.1nm,sm,nf
Lifetime use of alcohol and/or marijuana
<30 years	76.9	69.2–83.2sf	66.1	56.0–74.8	66.5	59.0–73.2sf	48.8	40.7–57.0nm,nf
30–39 years	73.7	64.6–81.2sf	74.6	64.5–82.6sf	75.7	66.6–83.0sf	42.9	33.9–52.4nm,sm,nf
40+ years	82.4	73.8–88.6sf	77.5	69.3–84.1sf	71.6	63.3–78.7sf	40.0	32.7–47.8nm,sm,nf
All ages	77.4	72.7–81.5sf	72.9	67.6–77.6sf	71.0	66.3–75.2sf	43.9	39.2–48.8nm,sm,nf
Lifetime combined substance use
<30 years	43.9	35.8–52.3sf	37.6	28.5–47.7sf,t	30.5	23.7–38.2	19.6	13.9–26.9nm,sm,t
30–39 years	39.5	30.9–48.8sf	33.6	24.5–44.1sf,t	36.0	27.3–45.7sf	12.6	7.6–20.2nm,sm,nf,t
40+ years	37.8	29.4–46.9sf	23.8	16.8–32.4sf,t	22.4	15.9–30.7sf	6.2	3.2–11.6nm,sm,nf,t
All ages	40.4	35.5–45.6sf	31.4	26.4–36.9sf	29.8	25.3–34.6nm,sf	12.8	9.8–16.4nm,sm,nf

Note: CI indicates confidence intervals calculated at the 99% level. The superscripts nm, sm, nf and sf indicate American Indian Northern Plains and Southwest males and Northern Plains and Southwest females, respectively, and are used to indicate significant (p < 0.01) pairwise comparisons between gender/culture groups. Statistically significant differences (p < 0.01) within one gender/culture group among the three age groups (<30 years, 30–39 years, 40+ years) are indicated through use of the superscript t. Lifetime combined substance use is lifetime use of both alcohol and marijuana.