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Table 6 Mean frequency of cannabis, meth/amphetamine and ecstasy use (95% confidence interval and sample size), for the intervention and control groups, over time

From: A universal harm-minimisation approach to preventing psychostimulant and cannabis use in adolescents: a cluster randomised controlled trial

   Baseline Post Five month follow-up 10 month follow-up
Frequency of cannabis use in last three months a Control 0.24 0.25 0.27 0.29
(0.18-0.30) (0.17-0.33) (0.19-0.35) (0.19-0.39)
(n = 823) (n = 579) (n = 447) (n = 403)
Intervention 0.12 0.15 0.22 0.16
(0.08-0.16) (0.09-0.21) (0.14-0.30) (0.10-0.22)
(n = 898) (n = 626) (n = 614) (n = 568)
Frequency of meth/amphetamine use in last 12 months b Control 0.12 0.13 0.09 0.10
(0.04-0.12) (0.02-0.10) (0.07-0.15) (0.07-0.15)
(n = 824) (n = 578) (n = 449) (n = 403)
Intervention 0.08 0.06 0.11 0.09
(0.04-0.12) (0.02-0.10) (0.07-0.15) (0.05-0.13)
(n = 904) (n = 628) (n = 614) (n = 569)
Frequency of ecstasy use in last 12 months b Control 0.15 0.18 0.16 0.12
(0.11-0.19) (0.12-0.24) (0.10-0.22) (0.10-0.22)
(n = 824) (n = 578) (n = 447) (n = 403)
Intervention 0.10 0.10 0.12 0.11
(0.06-0.14) (0.06-0.14) (0.08-0.16) (0.07-0.15)
(n = 904) (n = 628) (n = 614) (n = 569)
  1. aFrequency was coded as: 0 = Have not used in the last 3 months, 1 = About once a month, 2 = Less than once a week, 3 = About once a week, 4 = More than once a week (but less than daily), 5 = Once a day, 6 = More than once per day.
  2. bFrequency was coded as: 0 = Have not used in the last 12 months, 1 = once or twice a year, 2 = Every few months, 3 = About once a month, 4 = Once a week or more, 5 = every day.