1. A study is conducted to assess the efficacy of gabapentin for the treatment of epilepsy. The authors undertook a search of both the published and unpublished literature. After independent assessment of two authors, 33 of 107 papers meet inclusion criteria for the study. The authors describe the data from these studies but are unable to calculate a summary statistic because of the significant heterogeneity of the studies. Which of the following best describes the study design?

1. Case-control study
2. Meta-analysis
3. Narrative review
4. Randomized control trial
5. Systematic review