Allegiance effects in cognitive processing therapy (CPT) for posttraumatic stress disorder (PTSD): a systematic review and meta-analysis

Objective: We sought to determine whether there is evidence of researcher allegiance bias in the reporting of cognitive processing therapy (CPT) for posttraumatic stress disorder (PTSD). Method: We used a reprint analysis approach–whereby papers were coded for indications of potential bias–to determine the presence and magnitude of researcher allegiance in published randomized controlled trials (RCTs) of CPT. Results: Twenty trials met inclusion criteria. Evidence of allegiance to CPT rather than the respective comparison conditions was typically small to negligible. A meta-regression analysis of the 17 studies which included an active comparison group did not find an association between allegiance scores and study effect size for the reduction of PTSD symptoms (95% CI: −0.05, 0.19). Conclusion: There is no evidence at present that the CPT literature has been unduly influenced by allegiance held to CPT or the comparator conditions.