Skip to main content
. Author manuscript; available in PMC: 2021 Jul 1.
Published in final edited form as: Drug Alcohol Depend. 2020 May 18;212:108064. doi: 10.1016/j.drugalcdep.2020.108064

Table 1.

Slope Estimates for Historical Trends in Past 30-day Marijuana Use among 12th Grade U.S. Students, 1976–2019

N(total) Slope 1 (SE) pa JPb Slope 2 (SE) p JP Slope 3 (SE) p JP Slope 4 (SE) p
All students
 Any 30-day use 649,505 −3.429 (0.322) <0.001 1990–91 2.480 (1.941) 0.222 1996–97 0.023 (0.156) 0.885
 Frequent usec 649,505 −1.114 (0.103) <0.001 1990–91 0.972 (0.338) 0.012 1998–99 0.036 (0.073) 0.630
Lifetime users
 Any 30-day use 311,168 −4.311 (0.860) <0.001 1986–87 0.563 (0.179) 0.006
 Frequent use 311,168 −1.689 (0.154) <0.001 1990–91 2.321 (1.279) 0.091 1996–97 0.233 (0.107) 0.048
Lifetime users by sex
 Females 143,375 −1.581 (0.180) <0.001 1988–89 0.965 (0.292) 0.005 1998–99 0.139 (0.109) 0.224
 Males 154,189 −1.967 (0.203) <0.001 1990–91 2.835 (1.797) 0.137 1996–97 0.309 (0.135) 0.039
Lifetime users by race/ethnicity
 Black 31,913 −1.510 (0.154) <0.001 1990–91 2.315 (1.377) 0.115 1996–97 0.582 (0.130) <0.001
 Hispanic 28,188 −1.646 (0.283) <0.001 1988–89 1.180 (0.428) 0.019 1998–99 −0.395 (0.697) 0.582 2006–07 0.500 (0.183) 0.019
 White 216,733 −1.695 (0.183) <0.001 1990–91 2.428 (1.542) 0.138 1996–97 0.229 (0.143) 0.131
 Other 22,689 −2.366 (0.397) <0.001 1988–89 0.421 (0.088) <0.001

Notes: Bold font indicates slopes with t-test p-values <0.05.

a

p-values of the slope changes are calculated from t-tests based on asymptotic normality; the number of joinpoints is calculated using a permutation test procedure not requiring asymptotic normality and maintaining correct Type I error probability.

b

JP = Joinpoint, or year grouping in which significant change in slope occurred.

c

Frequent use defined as use on 20+ occasions in the past 30 days.