Project Choices Preconception Intervention: A Mediation Analysis of the Processes of Change

Background and Purpose: The purpose of the current study was to examine mechanisms of the treatment effect previously found for CHOICES (Floyd, et al. 2007), a motivational intervention to reduce the risk of alcohol exposed pregnancy (AEP) among women of childbearing age. Despite theoretical advancements and a burgeoning literature supporting the efficacy of MI, there is a need to understand the mechanisms through which MI-based interventions exert their effects. The current study addresses this gap with a prospective examination of mediating effects of the processes of change (POC) as proposed by the Transtheoretical Model (TTM). Results can inform future intervention development and variables to which both practitioners and research can relate.

CHOICES is grounded in the TTM, which posits 5 experiential and 5 behavioral POC. Experiential POC occur in the earlier stages of change, and are relevant to one’s thought processes and situational experiences. Behavioral POC occur in the later stages of change and are more action-oriented. Consistent with the TTM, we hypothesized that assignment to CHOICES at baseline would be positively associated with experiential POC at the 3-month follow-up time-point, which would, predict behavioral POC at the 9-month follow-up time-point, which would predict treatment outcome at 9 months. The treatment outcomes examined were risky drinking (RD), ineffective contraception (IEC), and AEP.

 Methods: We utilized data from the CHOICES efficacy study (Floyd, et al., 2007). 830 women at risk for AEP were randomized to receive either CHOICES or usual care Primary outcomes and proposed mediators (POC) were assessed at 3, 6, and 9 months. Path analyses using weighted least squares estimation with a mean- and variance- adjusted chi-square statistic were conducted.  Model fit was assessed by examining model chi-square, CFI and TLI > .90, and RMSEA < .08.  Indirect effects were estimated using MODEL INDIRECT (bootstrapped 95% CI, using 5,000 resamples). Analyses were performed separately for each of the three outcome variables. POC measures specific to RD and IEC were utilized in models predicting RD and IEC, respectively. POC measures for both RD and IEC were utilized in the model predicting AEP.

 Results: All model fit indices indicated good fit, and the indirect effect of treatment group on outcome via POC variables was significant for the models predicting RD and IEC. Consistent with hypotheses, treatment assignment was positively associated with experiential POC, which in turn was positively associated with behavioral POC, which predicted reduced risk of the outcome in the RD and EC models. The indirect effect of treatment group on AEP through EC processes was significant, but the indirect effect through RD processes was not. The direction of indirect effects for the AEP model was also consistent with hypotheses.

Conclusions and Implications: These findings support the temporal relationship between the experiential and behavioral POC consistent with the TTM that guided the CHOICES intervention.  Motivation-based interventions may benefit from directly targeting experiential POC early in treatment and behavioral POC later in treatment. Future research should examine the importance of POC in regards to other health behaviors.