The primary aim of this study was to determine whether different durations of contingency management (CM) in conjunction with psychosocial treatment produced different rates of abstinence among methamphetamine dependent individuals. Participants were randomized to one of the four 16-week treatment conditions: standard psychosocial treatment or psychosocial treatment plus one of the three durations of CM (one-month, two-month, or four-month). A total of 118 participants were randomized to the four treatment conditions. There were significant differences across treatment conditions for number of consecutive days of methamphetamine abstinence (p<0.05). These differences were in the hypothesized direction, as participants were more likely to remain abstinent through the 16-week trial as CM duration increased. A significant effect of treatment condition (p<0.05) and time (p<0.05) on abstinence over time was also found. Longer durations of CM were more effective for maintaining methamphetamine abstinence.
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