The Influence of Attrition in Evaluating the Efficacy and Effectiveness of Mindfulness-Based Interventions

While a large body of controlled empirical research has demonstrated the treatment efficacy of MBIs, whether these treatment effects are effective is less well-established. A significant hindrance lies within deviations from the original study protocol, as protocol deviation challenges the validity of an intervention. The present study explored methodological trends in how protocol deviation is dealt with in the mindfulness literature. Studies published between 2011 and 2016 were selected for the review based on the following inclusion criteria: (a) mindfulness is the main component of an intervention, (b) randomized and controlled intervention, (c) clinical sample, and (d) report of per-protocol and intention-to-treat statistical analysis. Review results indicate that mindfulness RCT studies suffer from relatively high rates of participant dropout and that statistical methods used to address protocol deviation may not be enough to control for the likelihood of bias. Furthermore, information regarding participants' decision to discontinue study participation is not properly collected and assessed in many studies. This lack of attention to protocol deviation may prevent translating treatment efficacy of MBIs into treatment effectiveness.