According to the retraction notice released by the journal last week, the paper contains “extensive verbatim use of text from other sources.”
How did this make it past the editors? The journal published the paper in 2012 — before it began screening papers for plagiarism, according to a spokesperson.
It has come to the attention of the PLOS ONE Editors that there are substantial overlaps between the text of this article and a number of previously published works by other authors, particularly in the Introduction and Discussion sections. Text was duplicated verbatim or with minor modifications from the sources listed below:
Farrell C, McAvoy H, Wilde J (2008) Tackling health inequalities: An all-Ireland approach to social determinants. Islandbridge, Dublin: Combat Poverty Agency Publication. (Reference 1 in the published article) 
Vendruscolo LF, Pamplona FA, Takahashi RN (2004) Strain and sex differences in the expression of nociceptive behavior and stress-induced analgesia in rats. Brain Res 1030: 277–283. doi: 10.1016/j.brainres.2004.10.016 (Reference 5 in the published article) 
Racine M, Tousignant-Laflamme Y, Kloda LA, Dion D, Dupuis G, et al. (2012) A systematic literature review of 10 years of research on sex/gender and pain perception–Part 2: Do biopsychosocial factors alter pain sensitivity differently in women and men? Pain 153: 619–35. doi: 10.1016/j.pain.2011.11.026 (Reference 17 in the published article) 
Sex differences in opioid-mediated pain inhibitory mechanisms during the interphase in the formalin test. 2007. Neuroscience. Volume 146, Issue 1, 25 April 2007, Pages 366–374 (uncited in the published article) 
The formalin test: a dose–response analysis at three developmental stages. 1998. Pain Volume 76, Issue 3, June 1998, Pages 337–347 (uncited in the published article) 
Glynn P, Coakley R, Kilgallen I, Murphy N, O’Neill S (1999) Circulating interleukin 6 and interleukin 10 in community acquired pneumonia. Thorax 54: 51–55. doi:10.1136/thx.54.1.51 (Reference 35 in the published article) 
Gioiosa L, Chiarotti F, Alleva E, Laviola G (2009) A trouble shared is a trouble halved: social context and status affect pain in mouse dyads. PloS one 4: e4143. doi:10.1371/journal.pone.0004143 (Reference 34 in the published article) 
Institute for Laboratory Animal Research (2009) Recognition and alleviation of pain in laboratory animals. In: Recognition and Assessment of Pain. Washington, D.C: National Academies Press. pp. 47–70. (Reference 16 in the published article) 
Spooner MF, Robichaud P, Carrier JC, Marchand S (2007) Endogenous pain modulation during the formalin test in estrogen receptor beta knockout mice. Neuroscience 150: 675–680. doi: 10.1016/j.neuroscience.2007.09.037 (Reference 40 in the published article) 
Ford GK, Finn DP (2008) Clinical correlates of stress-induced analgesia: evidence from pharmacological studies. Pain 140: 3–7. doi: 10.1016/j.pain.2008.09.023 (Reference 38 in the published article) 
Sternberg WF (1999) Sex differences in the effects of prenatal stress on stress-induced analgesia. Physiol Behav 68: 63–72. doi: 10.1016/s0031-9384(99)00164-x (Reference 22 in the published article) 
Klatzkin RR, Mechlin B, Girdler SS (2010) Menstrual cycle phase does not influence gender differences in experimental pain sensitivity. Eur J Pain 14: 77–82. doi:10.1016/j.ejpain.2009.01.002 (Reference 57 in the published article) 
In view of the extensive verbatim use of text from other sources, the PLOS ONE Editors retract this article.
The authors wish to acknowledge that such re-use of text is not appropriate and would like to apologize.
The paper has been cited once, according to Thomson Reuters Web of Science.
A spokesperson for PLOS told us:
The journal office was alerted to instances of overlap in the text of the article with that from other publications. Upon evaluation of the level of text overlap and consideration of COPE guidelines, the PLOS ONE editors reached the decision to retract the article. The manuscript was submitted in 2012, PLOS ONE has since implemented changes to the initial checks on submissions and currently all manuscripts are scanned via the Similarity Check software.
The authors are all based at Shahed University in Tehran. We could not find contact info for first author Marjan Aghajani, or last author Tooba Ghazanfari; an email to corresponding author Mohammad Reza Vaez Mahdavi bounced back.
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