Turning a blind eye: the success of blinding reported in a random sample of randomised, placebo controlled trials
Open accessAbstract
OBJECTIVE: To examine the reporting and success of double blinding in a sample of randomised, placebo controlled trials from leading general medicine and psychiatry journals. METHODS: Identification of placebo controlled, randomised controlled trials from prespecified general medical and psychiatric journals indexed on Medline between 1 January 1998 and 1 October 2001, from which a random sample of 200 randomised clinical trials was chosen, of which 191 trials were evaluated. RESULTS: Only seven of the 97 (7%) general medicine trials provided evidence on the success of blinding, with five reporting that the success of blinding was imperfect. In trials from psychiatric journals, the success of blinding was reported in eight of the 94 trials, with four reporting that the blinding was imperfect. Overall, only four of the 191 (2%) trials assessed blinding in the participants and either the outcome assessors or the investigators. CONCLUSIONS: The current lack of reporting on the success of blinding provides little evidence that success of blinding is maintained in placebo controlled trials. Trialists and editors should make a concerted effort to incorporate, report, and publish such information and its potential effect on study results.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
Most controlled trials do not adequately examine assessor blinding, even though it is widely considered a very important component of good study design.
“Most controlled trials do not adequately examine assessor blinding,53 even though it is widely considered a very important component of good study design.54”
Cites
The Revised CONSORT Statement for Reporting Randomized Trials: Explanation and Elaboration
Altman, D. G., Schulz, K. F., Moher, D., Egger, M., Davidoff, F., Elbourne, D., Gøtzsche, P. C., Lang, T., & for the CONSORT Group (2001) · Annals of Internal Medicine · doi:10.7326/0003-4819-134-8-200104170-00012 · Cited by 3,835 · see citing works
Omega 3 Fatty Acids in Bipolar Disorder: A Preliminary Double-blind, Placebo-Controlled Trial
Stoll, A. L., Severus, W. E., Freeman, M. P., Rueter, S., Zboyan, H. A., Diamond, E., Cress, K. K., & Marangell, L. B. (1999) · Archives of General Psychiatry · doi:10.1001/archpsyc.56.5.407 · Cited by 814 · see citing works
Sackeim, H. A., Haskett, R. F., Mulsant, B. H., Thase, M. E., Mann, J. J., Pettinati, H. M., Greenberg, R. M., Crowe, R. R., Cooper, T. B., & Prudic, J. (2001) · JAMA · doi:10.1001/jama.285.10.1299 · Cited by 686 · see citing works
The Effect of Dietary ω-3 Fatty Acids on Coronary Atherosclerosis
von Schacky, C., Angerer, P., Kothny, W., Theisen, K., & Mudra, H. (1999) · Annals of Internal Medicine · doi:10.7326/0003-4819-130-7-199904060-00003 · Cited by 487 · see citing works
Efficacy of High-Dose Glycine in the Treatment of Enduring Negative Symptoms of Schizophrenia
Heresco‐Levy, U., Javitt, D. C., Ermilov, M., Mordel, C., Silipo, G. S., & Lichtenstein, M. (1999) · Archives of General Psychiatry · doi:10.1001/archpsyc.56.1.29 · Cited by 487 · see citing works
Controversy in Counting and Attributing Events in Clinical Trials
Sackett, D. L., & Gent, M. (1979) · New England Journal of Medicine · doi:10.1056/nejm197912273012602 · Cited by 413 · see citing works
Apfel, S. C., Schwartz, S., Adornato, B. T., Freeman, R. L., Biton, V., Rendell, M., Vinik, A. I., Giuliani, M. J., Stevens, J. C., Barbano, R. L., et al. (2000) · JAMA · doi:10.1001/jama.284.17.2215 · Cited by 366 · see citing works
Intention-to-treat analysis and the goals of clinical trials*
Sheiner, L. B., & Rubin, D. B. (1995) · Clinical Pharmacology & Therapeutics · doi:10.1016/0009-9236(95)90260-0 · Cited by 315 · see citing works
Shlay, J. C. (1998) · JAMA · doi:10.1001/jama.280.18.1590 · Cited by 307 · see citing works
Devereaux, P. J. (2001) · JAMA · doi:10.1001/jama.285.15.2000 · Cited by 258 · see citing works
The Landscape and Lexicon of Blinding in Randomized Trials
Schulz, K. F., Chalmers, I., & Altman, D. G. (2002) · Annals of Internal Medicine · doi:10.7326/0003-4819-136-3-200202050-00022 · Cited by 242 · see citing works
Blöndal, T., Gudmundsson, L. J., Olafsdottir, I., GUSTAVSSON, G., Westin, Å., & Stapleton, J. (1999) · BMJ · doi:10.1136/bmj.318.7179.285 · Cited by 218 · see citing works
Prevention of Recurrent Postpartum Depression
Wisner, K. L., Perel, J. M., Peindl, K., Hanusa, B. H., Findling, R. L., & RAPPORT, D. J. (2001) · The Journal of Clinical Psychiatry · doi:10.4088/jcp.v62n0202 · Cited by 180 · see citing works
Schulz, K. F., Grimes, D. A., Altman, D. G., & Hayes, R. J. (1996) · BMJ · doi:10.1136/bmj.312.7033.742 · Cited by 163 · see citing works
Rowe, P. C., Calkins, H., DeBusk, K., McKenzie, R., Anand, R., Sharma, G., Cuccherini, B. A., Soto, N., Hohman, P., Snader, S., et al. (2001) · JAMA · doi:10.1001/jama.285.1.52 · Cited by 142 · see citing works
Placebo-controlled trial of moclobemide in social phobia
Schneier, F. R., Goetz, D. M., Campeas, R. B., Marshall, R. D., Fallon, B., & Liebowitz, M. R. (1998) · The British Journal of Psychiatry · doi:10.1192/bjp.172.1.70 · Cited by 139 · see citing works
Treatment of Premenstrual Dysphoric Disorder With Sertraline During the Luteal Phase
Young, S. A., Hurt, P. H., Benedek, D. M., & Howard, R. S. (1998) · The Journal of Clinical Psychiatry · doi:10.4088/jcp.v59n0206 · Cited by 136 · see citing works
Effect of Alcohol on Social Phobic Anxiety
Himle, J. A., Abelson, J. L., Haghightgou, H., Hill, E. M., Nesse, R. M., & Curtis, G. C. (1999) · American Journal of Psychiatry · doi:10.1176/ajp.156.8.1237 · Cited by 78 · see citing works
Enhancement of CO2-Induced Anxiety in Healthy Volunteers With the Serotonin Antagonist Metergoline
Ben-Zion, I., Meiri, G., Greenberg, B. D., Murphy, D. L., & Benjamin, J. (1999) · American Journal of Psychiatry · doi:10.1176/ajp.156.10.1635 · Cited by 36 · see citing works
Evaluating the use of benzodiazepines following recent bereavement
Warner, J. P., Metcalfe, C. D., & King, M. (2001) · The British Journal of Psychiatry · doi:10.1192/bjp.178.1.36 · Cited by 30 · see citing works
Sandler, R. S., Zorich, N. L., Filloon, T. G., et al. (1999) · Annals of Internal Medicine · doi:10.7326/0003-4819-130-4_part_1-199902160-00002 · Cited by 25 · see citing works
Moncrieff, J., & Double, D. B. (2003) · PubMed · Cited by 7 · see citing works
Flagged first, then by citations
Cited by
Sorted by citations
SPIRIT 2013 explanation and elaboration: guidance for protocols of clinical trials
Chan, A.-W., Tetzlaff, J. M., Gotzsche, P. C., Altman, D. G., Mann, H., Berlin, J. A., Dickersin, K., Hrobjartsson, A., Schulz, K. F., Parulekar, W. R., et al. (2013) · BMJ · doi:10.1136/bmj.e7586 · Cited by 6,251 · see citing works
Assessing Risk of Bias in Included Studies
Higgins, J. P., & Altman, D. G. (2008) · Cochrane Handbook for Systematic Reviews of Interventions · doi:10.1002/9780470712184.ch8 · Cited by 3,396 · see citing works
Moher, D., Hopewell, S., Schulz, K. F., Montori, V., Gøtzsche, P. C., Devereaux, P. J., Elbourne, D., Egger, M., & Altman, D. G. (2012) · International Journal of Surgery · doi:10.1016/j.ijsu.2011.10.001 · Cited by 2,345 · see citing works
Moher, D., Hopewell, S., Schulz, K. F., Montori, V., Gøtzsche, P. C., Devereaux, P. J., Elbourne, D., Egger, M., & Altman, D. G. (2010) · Journal of Clinical Epidemiology · doi:10.1016/j.jclinepi.2010.03.004 · Cited by 1,858 · see citing works
Borrelli, B., Sepinwall, D., Ernst, D., Bellg, A. J., Czajkowski, S., Breger, R., DeFrancesco, C., Levesque, C., Sharp, D. L., Ogedegbe, G., et al. (2005) · Journal of Consulting and Clinical Psychology · doi:10.1037/0022-006x.73.5.852 · Cited by 803 · see citing works
A Trial of Sugar-free or Sugar-Sweetened Beverages and Body Weight in Children
de Ruyter, J. C., Olthof, M. R., Seidell, J. C., & Katan, M. B. (2012) · New England Journal of Medicine · doi:10.1056/nejmoa1203034 · Cited by 814 · see citing works
Reporting methods of blinding in randomized trials assessing nonpharmacological treatments
Boutron, I., Guittet, L., Estellat, C., Moher, D., Hróbjartsson, A., & Ravaud, P. (2007) · PLoS Medicine · doi:10.1371/journal.pmed.0040061 · Cited by 389 · see citing works
Blinding and expectancy confounds in psychedelic randomized controlled trials
Muthukumaraswamy, S. D., Forsyth, A., & Lumley, T. (2021) · Expert Review of Clinical Pharmacology · doi:10.1080/17512433.2021.1933434 · Cited by 324 · see citing works
Brunoni, A. R., Lopes, M., Kaptchuk, T. J., & Fregni, F. (2009) · PLoS ONE · doi:10.1371/journal.pone.0004824 · Cited by 173 · see citing works
SPIRIT 2025 explanation and elaboration: updated guideline for protocols of randomised trials
Hróbjartsson, A., Boutron, I., Hopewell, S., Moher, D., Schulz, K. F., Collins, G. S., Tunn, R., Aggarwal, R., Berkwits, M., Berlin, J. A., et al. (2025) · BMJ · doi:10.1136/bmj-2024-081660 · Cited by 171 · see citing works
Self-citationCommentary: Measuring the success of blinding in RCTs: don't, must, can't or needn't?
Sackett, D. L. (2007) · International Journal of Epidemiology · doi:10.1093/ije/dym088 · Cited by 150 · see citing works
Juul, S., Gluud, C., Simonsen, S., Frandsen, F. W., Kirsch, I., & Jakobsen, J. C. (2021) · BMJ Evidence-Based Medicine · doi:10.1136/bmjebm-2020-111407 · Cited by 135 · see citing works
Sharma, S., Jensen, M. P., Moseley, G. L., & Abbott, J. H. (2019) · BMJ Open · doi:10.1136/bmjopen-2018-026874 · Cited by 61 · see citing works
Fool’s gold? Why blinded trials are not always best
Anand, Norrie, Bradley, McAuley, & Clarke (2020) · BMJ · doi:10.1136/bmj.l6228 · Cited by 58 · see citing works
Lowe, C. M., Wilson, M., Sackley, C., & Barker, K. (2011) · Clinical Rehabilitation · doi:10.1177/0269215510380824 · Cited by 50 · see citing works
Vickrey, B. G., Mittman, B. S., Connor, K. I., Pearson, M. L., Della Penna, R. D., Ganiats, T. G., DeMonte, R. W., Chodosh, J., Cui, X., Vassar, S., et al. (2006) · Annals of Internal Medicine · doi:10.7326/0003-4819-145-10-200611210-00004 · Cited by 44 · see citing works
Ten Practical Recommendations for Improving Blinding Integrity and Reporting in Psychotherapy Trials
Mataix-Cols, D., & Andersson, E. (2021) · JAMA Psychiatry · doi:10.1001/jamapsychiatry.2021.1419 · Cited by 23 · see citing works
Blinding and expectancy confounds in psychedelic randomised controlled trials
Muthukumaraswamy, S., Forsyth, A., & Lumley, T. (2021) · doi:10.31234/osf.io/q2hzm · Cited by 15 · see citing works
van der Ende, N. A., Roozenbeek, B., Broderick, J. P., Khatri, P., Lingsma, H. F., & Dippel, D. W. (2023) · International Journal of Stroke · doi:10.1177/17474930221131706 · Cited by 14 · see citing works
- Authors
- Fergusson, D.
- Corresponding author
- Fergusson, D.
- ORCID
- Fergusson, D.
- Venue
- BMJ
- Publisher
- BMJ
- Published
- 2004-02-21
- Volume
- 328
- Issue
- 7437
- Pages
- 432-0
- ISSN
- 0007-1447 (ISSN-L)
- 0959-8138
- 1468-5833
- PMC
- PMC344259
- OpenAlex
- W2138919074
- Cited by
- 264
- References
- 23
- Citations by year
- 2026: 3 · 2025: 11 · 2024: 10 · 2023: 9 · 2022: 15 · 2021: 14 · 2020: 9 · 2019: 7 · 2018: 15 · 2017: 6 · 2016: 8 · 2015: 8 · 2014: 6 · 2013: 13 · 2012: 15
- FWCI
- 21.67
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- BMJ (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- HighWire Press Open Archive (submittedVersion)
- DigitalGeorgetown (Georgetown University Library) (submittedVersion)
- Topics
- Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmacology › Pharmaceutical industry and healthcare
- Keywords
- blinding, double blinding, randomized controlled trials, trial reporting quality, general medicine journals, psychiatric journals
- MeSH terms
- Double-Blind Method, Randomized Controlled Trials as Topic
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review