The original study used an intention-to-treat (ITT) model, in which all randomized participant outcomes are analyzed according to the group to which they were assigned. This model revealed no reduction in stimulant use for the exercise vs. health education groups as a whole.
However, because many participants in the exercise group did not exercise at the prescribed dose, researchers applied a secondary complier average causal effects (CACE) analysis to the data to see if amount (or “dose”) of exercise made any difference in terms of outcomes.
Participants in the study were sedentary but medically approved for exercise, used stimulants within 30 days prior to study entry, and received a DSM-IV stimulant abuse or dependence diagnosis within the past year. A CACE analysis was adjusted to include only participants with a minimum threshold of adherence to the exercise dose (at least 8.3 KWW). A negative-binomial hurdle model was used to provide estimates of probability of stimulant use (i.e., relapse) and amount of use among those who used.
Unlike the ITT model in the original study, which found no benefit to exercise compared to health education for stimulant use disorder treatment, the CACE-adjusted analysis found that exercising at an adequate dose significantly lowered probability of relapse to stimulant use compared to receiving health education (41% vs. 55.7%) and also significantly lowered days of stimulant use among those who did relapse (5 days vs. 9.9 days).
Conclusions: Together, these results -- lowered risk of relapse and lowered days of use after relapse -- suggest a beneficial effect of adequate levels of exercise in the treatment of stimulant abuse. Further research is warranted to develop strategies for exercise adherence that can ensure achievement of an exercise dose sufficient to produce a significant treatment effect.
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Funding for this Addiction Science Made Easy project is provided by the Addiction Technology Transfer Center National Office, under the cooperative agreement from the Center for Substance Abuse Treatment of SAMHSA.
Articles were written based on the following published research:
Carmody T, et al. A Complier Average Causal Effect Analysis of the Stimulant Reduction Intervention using Dosed Exercise Study. Contemporary Clinical Trials Communications 2018