CRD Summary: The authors concluded that limited evidence suggested that valproate may be effective for the treatment of post-traumatic stress disorder and that further research is required. There were limitations to this review, but overall the authors’ conclusions reflected limited evidence from a small number of poor quality studies.

CRD Commentary: The review question was clearly stated and inclusion criteria were defined for participants, outcome and intervention. The criteria for study design were broad, which appeared appropriate given the paucity of identified studies. Several relevant sources were searched and attempts were made to minimise publication and language bias. Study validity was assessed using defined criteria and, although results were mainly reported as an aggregate score, some methodological flaws were summarised in the discussion, including the problem of attrition bias when calculating before and after effect size from aggregate data. Appropriate methods were used to minimise reviewer error and bias in the assessment of study validity, but it was not clear if similar methods were used to select studies for inclusion in the review or extract data. In view of the clinical heterogeneity among studies, particularly with respect to outcome measures, it was questionable if pooling data statistically was appropriate. There were limitations to this review, but overall the authors’ cautious conclusions reflected limited evidence from a small number of poor quality studies.