Edmond Edi‐Osagie contributed to designing the review, publishing the protocol, data collection, developing a search strategy, undertaking searches, screening search results, organising retrieval of papers, screening retrieved papers against inclusion criteria, appraising quality of papers, abstracting data from papers, writing to authors of papers for additional information, data management for the review, interpretation of data, providing a methodological perspective, providing a clinical perspective, providing a policy perspective, writing the review, providing general advice on the review, and performing previous work that was the foundation of the review.

Lee Hooper developed the second search strategy, undertook the February 2002 searches, screened these search results, assessed inclusion of all potential studies, appraised the quality of, and abstracted data from, all included studies, analysed the data (meta‐analysis in RevMan, subgrouping, sensitivity analyses, meta‐regression in STATA), interpreted the data, provided a methodological perspective, provided a consumer perspective, wrote the methodology and results sections of the review and edited the final review.

Phil McGinlay contributed to designing the review, data collection for the review, developing a search strategy, undertaking searches, screening search results, organising retrieval of papers, screening retrieved papers against inclusion criteria, and appraising quality of papers. Mr. McGinlay unfortunately passed away before completion of this review.

Mourad Seif contributed to conceiving the review, designing the review, publishing the protocol, coordinating the review, data collection for the review, developing a search strategy, undertaking searches, screening search results, organising retrieval of papers, screening retrieved papers against inclusion criteria, arbitration on quality and data extraction of papers, interpretation of data, providing a methodological perspective, providing a clinical perspective, providing a policy perspective, editing the review, providing general advice on the review, and performing previous work that was the foundation of the review.

Cindy Farquhar updated the review in July 2005 by completing the new searches, selecting the studies, restructuring the table of comparisons, extracting the data and rewriting parts of the review.

Debbie Blake was involved in the 2005 update by cross checking newly extracted data, assessing inclusion criteria, subgroup analysis, editing and providing a scientific perspective to the updated text.