Unpublished or "zombie" reviews (the file-drawer effect)

This problem is not addressed in any checklist or guideline. Systematic reviews may be registered or conducted without being published, often due to a lack of statistically significant findings. These are sometimes called "zombie reviews" which are kept in the file drawer as they can be more difficult to publish. This contributes to publication bias as well as research waste.

Articles that support this problem:

Unpublished systematic reviews and financial support: a meta-epidemiological study

2017 : Bmc research notes

Reporting bias in the literature on the associations of health-related behaviors and statins with cardiovascular disease and all-cause mortality

2018 : Plos biology

More systematic reviews were registered in PROSPERO each year, but few records’ status was up-to-date

2020 : Journal of clinical epidemiology

Half of systematic reviews about pain registered in PROSPERO were not published and the majority had inaccurate status

2019 : Journal of clinical epidemiology

An international survey indicated that unpublished systematic reviews exist

2009 : Journal of clinical epidemiology

Following 411 Cochrane protocols to completion: a retrospective cohort study

2008 : Plos one

Factors predicting completion and time to publication of Cochrane reviews

2009 : Open medicine

Deficiencies in the publication and reporting of the results of systematic reviews presented at scientific medical conferences

2015 : Journal of clinical epidemiology

Following Cochrane review protocols to completion 10 years later: a retrospective cohort study and author survey

2019 : Journal of clinical epidemiology

Cochrane systematic reviews for the mental health field: is the gold standard tarnished?

2013 : Psychiatric services

The fate of urological systematic reviews registered in PROSPERO

2019 : World journal of urology

Zombie reviews taking over the PROSPERO systematic review registry. It’s time to fight back!

2019 : British journal of sports medicine

Characteristics, completion and publication of PROSPERO records in regional anesthesia for acute perioperative pain

2023 : Journal of comparative effectiveness research