No pets allowed: Evidence that prolonged grief disorder can occur following the death of a pet

Philip Hyland

doi:10.1371/journal.pone.0339213

Peer Review History

Original SubmissionSeptember 25, 2025
5 Nov 2025 Decision Letter - Jose A. Calvache, Editor Dear Dr. Hyland, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Dec 20 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'. If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols . Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols . We look forward to receiving your revised manuscript. Kind regards, Jose A. Calvache, MD, MSc, PhD Academic Editor PLOS ONE Journal Requirements: When submitting your revision, we need you to address these additional requirements. 1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf 2. Please note that your Data Availability Statement is currently missing the repository name. If your manuscript is accepted for publication, you will be asked to provide these details on a very short timeline. We therefore suggest that you provide this information now, though we will not hold up the peer review process if you are unable. 3. When completing the data availability statement of the submission form, you indicated that you will make your data available on acceptance. We strongly recommend all authors decide on a data sharing plan before acceptance, as the process can be lengthy and hold up publication timelines. Please note that, though access restrictions are acceptable now, your entire data will need to be made freely accessible if your manuscript is accepted for publication. This policy applies to all data except where public deposition would breach compliance with the protocol approved by your research ethics board. If you are unable to adhere to our open data policy, please kindly revise your statement to explain your reasoning and we will seek the editor's input on an exemption. Please be assured that, once you have provided your new statement, the assessment of your exemption will not hold up the peer review process. 4. If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise. 5. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice. Additional Editor Comments: Dear authots, The study employed a cross-sectional online survey design, which is appropriate for descriptive and comparative purposes; however, such a design inherently limits the ability to draw causal inferences or make definitive diagnostic claims. The use of the International Grief Questionnaire with “clinical checks” (IGQ-CC) was methodologically sound and supported by previous literature demonstrating strong psychometric properties. Nonetheless, its cross-cultural validity has not been specifically established for cases of pet loss, which may limit the generalizability of the findings. The diagnosis of Prolonged Grief Disorder (PGD) was based solely on self-reported measures without clinical confirmation or structured interviews, which could lead to over- or underestimation of actual cases. Despite this limitation, the measurement of the construct remains psychometrically supported. Thanks for the submission. The statistical analyses were clearly described and appropriate to the study’s objectives; however, the absence of multivariate models controlling for demographic variables—such as age, gender, education, type of pet, or time since the loss—restricts the interpretability of the reported associations and precludes conclusions about potential confounding effects. The data presented are coherent and support the central finding that symptoms of PGD may also manifest following the death of a pet. Nonetheless, the study’s conclusions should remain interpretive rather than prescriptive, as the evidence—derived from a single cross-sectional, self-report design—does not provide a sufficient basis for causal claims or for advocating diagnostic manual revisions. i suggest to avoid any causal claims and present your study as descritive modelling with an interesting and provocative result. [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? Reviewer #1: Yes Reviewer #2: Yes ******** 2. Has the statistical analysis been performed appropriately and rigorously? -->?> Reviewer #1: Yes Reviewer #2: Yes ****** 3. Have the authors made all data underlying the findings in their manuscript fully available??> The PLOS Data policy Reviewer #1: Yes Reviewer #2: Yes ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English??> Reviewer #1: Yes Reviewer #2: Yes ****** Reviewer #1: CONSIDERATIONS: � The subject is treated in a complete way; the article is solid. � It has a scientific interest, complements the existing information in literature, the original contributions are well achieved. � The results are well elaborated, the discussion and conclusions are strong, their contribution is important to the existing literature. � There is overall coherence in the development of the article. � The references are written in Vancouver style; however, I did not find the referencing in the text, the bibliography is not listed. � The wording is clear and precise. � The figures and tables are understandable, I suggest reworking figure 1, it looks pixelated. � The methodology is well constructed, a remark is made in the "notes" section. � The discussion is good and well structured, clinically relevant issues are discussed. � It is a novel and necessary issue to generate an update of the definition of PGD in future consensus. NOTES: � Page 8: Scores ≥ to… (¿?), incomplete information. � The study uses the cultural criterion of PGD (symptoms that exceed what is normal in the participant's social/cultural/religious context). It is noted in a footnote that a strict reading of ICD-11 could exclude cases that answered, "I don't know" (16.6%, n=137), but that previous studies followed that only excluded those that answered "No". The rationale for this decision (including n=137) should be moved to the methods section and discussed further as a limitation or a key methodological decision. The impact of strict exclusion of these cases on PGD rates should be briefly considered in the Discussion. � I suggest mentioning as a limitation the fact that the selection of participants from online research panels (Qualtrics) could bias the results (for example, towards those with greater digital access or certain demographic trends not covered by quotas). Reviewer #2: The research utilizes a cross-sectional approach through an online survey, which is suitable for both descriptive and comparative aims. Nevertheless, this kind of design does not permit causal conclusions or conclusive diagnostic claims. Concerning the instrument utilized, the use of the International Grief Questionnaire with “clinical checks” is suitable and backed by prior literature highlighting its strong psychometric characteristics. However, it is crucial to highlight that the cross-cultural validity of the IGQ-CC was not confirmed for the particular situation of pet loss, which could restrict the applicability of the results. The diagnosis of Prolonged Grief Disorder depended solely on self-reported assessments, lacking clinical validation or organized interviews. This methodological constraint might result in either an overcount or an undercount of real cases. Nonetheless, the measurement of the construct is regarded as reliable and backed by previous psychometric findings. The statistical methods are clearly outlined and deemed suitable for the objectives specified. Nevertheless, multivariate analyses were not performed to account for possible demographic covariates—like age, gender, education level, type of pet, or time since the loss—thus restricting the interpretation of relative risk estimates and the accuracy of the reported associations. The data provided are coherent and back the study's key findings, especially the point that PGD symptoms can also arise after the passing of a pet. However, the normative or prescriptive conclusions—like the recommendation to revise international diagnostic manuals—lack adequate empirical backing, particularly since the results stem from a solitary cross-sectional self-report study. The manuscript ultimately details ethical approval and quality control protocols implemented during data collection. It further shows that the data can be accessed publicly on OSF, and the authors state that there are no conflicts of interest or external funding, thereby adhering to the journal's ethical and transparency requirements. ****** what does this mean? ). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy Reviewer #1: No Reviewer #2: No ******** [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] To ensure your figures meet our technical requirements, please review our figure guidelines: https://journals.plos.org/plosone/s/figures You may also use PLOS’s free figure tool, NAAS, to help you prepare publication quality figures: https://journals.plos.org/plosone/s/figures#loc-tools-for-figure-preparation. NAAS will assess whether your figures meet our technical requirements by comparing each figure against our figure specifications. Attachments Attachment Submitted filename: renamed_95a88.docx https://doi.org/10.1371/journal.pone.0339213.r001
Revision 1
14 Nov 2025 Author Response Editor comments: 1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. Reply: The documents on style requirements have been reviewed, and every effort have been made to ensure that the manuscript is presented in-line with the journal requirements. 2. Please note that your Data Availability Statement is currently missing the repository name. If your manuscript is accepted for publication, you will be asked to provide these details on a very short timeline. We therefore suggest that you provide this information now, though we will not hold up the peer review process if you are unable. Reply: The dataset has been uploaded to a publicly accessible OSF page where it can be downloaded. We have added the following to the manuscript in the methods section: “The dataset used for this study is publicly available on the Open Science Framework (https://osf.io/hymd4/overview).” 3. When completing the data availability statement of the submission form, you indicated that you will make your data available on acceptance. We strongly recommend all authors decide on a data sharing plan before acceptance, as the process can be lengthy and hold up publication timelines. Please note that, though access restrictions are acceptable now, your entire data will need to be made freely accessible if your manuscript is accepted for publication. This policy applies to all data except where public deposition would breach compliance with the protocol approved by your research ethics board. If you are unable to adhere to our open data policy, please kindly revise your statement to explain your reasoning and we will seek the editor's input on an exemption. Please be assured that, once you have provided your new statement, the assessment of your exemption will not hold up the peer review process. Reply: As above, the dataset has been uploaded to a publicly accessible OSF webpage and a link to the dataset is included in the manuscript. 4. If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise. Reply: Noted. 5. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice. Reply: Noted. Additional Editor Comments: Dear authors, The study employed a cross-sectional online survey design, which is appropriate for descriptive and comparative purposes; however, such a design inherently limits the ability to draw causal inferences or make definitive diagnostic claims. The use of the International Grief Questionnaire with “clinical checks” (IGQ-CC) was methodologically sound and supported by previous literature demonstrating strong psychometric properties. Nonetheless, its cross-cultural validity has not been specifically established for cases of pet loss, which may limit the generalizability of the findings. The diagnosis of Prolonged Grief Disorder (PGD) was based solely on self-reported measures without clinical confirmation or structured interviews, which could lead to over- or underestimation of actual cases. Despite this limitation, the measurement of the construct remains psychometrically supported. Thanks for the submission. The statistical analyses were clearly described and appropriate to the study’s objectives; however, the absence of multivariate models controlling for demographic variables—such as age, gender, education, type of pet, or time since the loss—restricts the interpretability of the reported associations and precludes conclusions about potential confounding effects. The data presented are coherent and support the central finding that symptoms of PGD may also manifest following the death of a pet. Nonetheless, the study’s conclusions should remain interpretive rather than prescriptive, as the evidence—derived from a single cross-sectional, self-report design—does not provide a sufficient basis for causal claims or for advocating diagnostic manual revisions. I suggest to avoid any causal claims and present your study as descriptive modelling with an interesting and provocative result. Reply: Duly noted, and great care has been taken in the revision phase to ensure that all language used, and conclusions drawn, fairly and accurately reflect the methodological design of the study. Reviewer #1: CONSIDERATIONS: The subject is treated in a complete way; the article is solid. Reply: Thank you. It has a scientific interest, complements the existing information in literature, the original contributions are well achieved. Reply: Thank you. The results are well elaborated, the discussion and conclusions are strong, their contribution is important to the existing literature. Reply: Thank you. There is overall coherence in the development of the article. Reply: Thank you. The references are written in Vancouver style; however, I did not find the referencing in the text, the bibliography is not listed. Reply: The references have been checked and now match the journal requirements. The wording is clear and precise. Reply: Thank you. The figures and tables are understandable, I suggest reworking figure 1, it looks pixelated. Reply: Figure 1 on my end looks clear and detailed. I am happy to work with the editor to ensure that the figure resolution is of the highest possible standard. The methodology is well constructed, a remark is made in the "notes" section. Reply: Thank you. The footnote has been moved into the text of the methods based on the request of reviewer 2. The discussion is good and well structured, clinically relevant issues are discussed. Reply: Thank you. It is a novel and necessary issue to generate an update of the definition of PGD in future consensus. Reply: Thank you. Page 8: Scores ≥ to… (¿?), incomplete information. Reply: This is now updated to note that scores >= 2 indicate symptom presence. The study uses the cultural criterion of PGD (symptoms that exceed what is normal in the participant's social/cultural/religious context). It is noted in a footnote that a strict reading of ICD-11 could exclude cases that answered, "I don't know" (16.6%, n=137), but that previous studies followed that only excluded those that answered "No". The rationale for this decision (including n=137) should be moved to the methods section and discussed further as a limitation or a key methodological decision. The impact of strict exclusion of these cases on PGD rates should be briefly considered in the Discussion. Reply: Noted, this change has been made to the manuscript. I suggest mentioning as a limitation the fact that the selection of participants from online research panels (Qualtrics) could bias the results (for example, towards those with greater digital access or certain demographic trends not covered by quotas). Reply: This has been added to the limitations, specifically to the first limitation where the limits of generalizability are discussed. Reviewer #2 comments: The research utilizes a cross-sectional approach through an online survey, which is suitable for both descriptive and comparative aims. Nevertheless, this kind of design does not permit causal conclusions or conclusive diagnostic claims. Concerning the instrument utilized, the use of the International Grief Questionnaire with “clinical checks” is suitable and backed by prior literature highlighting its strong psychometric characteristics. However, it is crucial to highlight that the cross-cultural validity of the IGQ-CC was not confirmed for the particular situation of pet loss, which could restrict the applicability of the results. Reply: Noted, and a sentence has been added to the limitations section: “Third, the IGQ-CC was used to measure PGD symptoms in this study, and psychometric support for this scale has only ever been obtained in samples of human bereaved individuals, prior to this study.” The diagnosis of Prolonged Grief Disorder depended solely on self-reported assessments, lacking clinical validation or organized interviews. This methodological constraint might result in either an overcount or an undercount of real cases. Nonetheless, the measurement of the construct is regarded as reliable and backed by previous psychometric findings. Reply: Thank you. The statistical methods are clearly outlined and deemed suitable for the objectives specified. Nevertheless, multivariate analyses were not performed to account for possible demographic covariates—like age, gender, education level, type of pet, or time since the loss—thus restricting the interpretation of relative risk estimates and the accuracy of the reported associations. Reply: I see the point, but the research questions under investigation did not necessitate covariate adjustment. The data provided are coherent and back the study's key findings, especially the point that PGD symptoms can also arise after the passing of a pet. However, the normative or prescriptive conclusions—like the recommendation to revise international diagnostic manuals—lack adequate empirical backing, particularly since the results stem from a solitary cross-sectional self-report study. Reply: Good point. The rather extreme statement at the end of the discussion that the diagnostic requirements should changed has been deleted. The manuscript ultimately details ethical approval and quality control protocols implemented during data collection. It further shows that the data can be accessed publicly on OSF, and the authors state that there are no conflicts of interest or external funding, thereby adhering to the journal's ethical and transparency requirements. Reply: Thank you. Attachments Attachment Submitted filename: Response to Reviewer Comments.docx https://doi.org/10.1371/journal.pone.0339213.r002
2 Dec 2025 Decision Letter - Jose A. Calvache, Editor No pets allowed: Evidence that prolonged grief disorder can occur following the death of a pet PONE-D-25-52202R1 Dear Dr. Hyland, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. For questions related to billing, please contact billing support . If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Jose A. Calvache, MD, MSc, PhD Academic Editor PLOS ONE Additional Editor Comments (optional): We would like to thank the authors for their thorough revisions and for providing comprehensive answers to all of the reviewers' questions and comments. The article now meets the high standards of the journal and is accepted for publication. Congratulations! Reviewers' comments: https://doi.org/10.1371/journal.pone.0339213.r003
Formally Accepted
Acceptance Letter - Jose A. Calvache, Editor PONE-D-25-52202R1 PLOS One Dear Dr. Hyland, I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS One. Congratulations! Your manuscript is now being handed over to our production team. At this stage, our production department will prepare your paper for publication. This includes ensuring the following: * All references, tables, and figures are properly cited * All relevant supporting information is included in the manuscript submission, * There are no issues that prevent the paper from being properly typeset You will receive further instructions from the production team, including instructions on how to review your proof when it is ready. Please keep in mind that we are working through a large volume of accepted articles, so please give us a few days to review your paper and let you know the next and final steps. Lastly, if your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. You will receive an invoice from PLOS for your publication fee after your manuscript has reached the completed accept phase. If you receive an email requesting payment before acceptance or for any other service, this may be a phishing scheme. Learn how to identify phishing emails and protect your accounts at https://explore.plos.org/phishing. If we can help with anything else, please email us at customercare@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Jose A. Calvache Academic Editor PLOS One https://doi.org/10.1371/journal.pone.0339213.r004

Open letter on the publication of peer review reports

PLOS recognizes the benefits of transparency in the peer review process. Therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. Reviewers remain anonymous, unless they choose to reveal their names.

We encourage other journals to join us in this initiative. We hope that our action inspires the community, including researchers, research funders, and research institutions, to recognize the benefits of published peer review reports for all parts of the research system.

Learn more at ASAPbio .