The association between diet and mental health and wellbeing in young adults within a biopsychosocial framework

Verena Rossa-Roccor; Chris G. Richardson; Rachel A. Murphy; Anne M. Gadermann

doi:10.1371/journal.pone.0252358

Peer Review History

Original SubmissionDecember 19, 2020
18 Feb 2021 Decision Letter - Sıdıka Bulduk, Editor PONE-D-20-39899 The association between diet and mental health and wellbeing in young adults within a biopsychosocial framework PLOS ONE Dear Dr. Rossa-Roccor, 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. I am very much thankful to the reviewers for their deep and thorough review. The article requires a major revision by referring to the reviewer's comments. Statistical analysis should be done appropriately and meticulously. Please submit your revised manuscript by Mar 25 2021 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. 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Please know it is PLOS ONE policy for corresponding authors to declare, on behalf of all authors, all potential competing interests for the purposes of transparency. PLOS defines a competing interest as anything that interferes with, or could reasonably be perceived as interfering with, the full and objective presentation, peer review, editorial decision-making, or publication of research or non-research articles submitted to one of the journals. Competing interests can be financial or non-financial, professional, or personal. Competing interests can arise in relationship to an organization or another person. Please follow this link to our website for more details on competing interests: http://journals.plos.org/plosone/s/competing-interests 5. We noted in your submission details that a portion of your manuscript may have been presented or published elsewhere. "This manuscript is based on the Master’s thesis of the corresponding author, Verena Rossa-Roccor. The thesis has been published at the UBC Theses and Dissertation Collection. A shortened version of the thesis has been published in the form of a report for stakeholders and knowledge users with the UBC food system and wellbeing operations in the UBC Sustainability Library." Please clarify whether this [conference proceeding or publication] was peer-reviewed and formally published. If this work was previously peer-reviewed and published, in the cover letter please provide the reason that this work does not constitute dual publication and should be included in the current manuscript. [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? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: No Reviewer #3: Partly ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes Reviewer #3: No ****** 3. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes Reviewer #3: Yes ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes Reviewer #3: Yes ****** 5. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: The manuscript has got an interesting topic and an appropriate methodology. It was written intelligibly in general. Also, the authors highlighted its limitations fairly. I believe that will contribute to the literature on this topic. Reviewer #2: This manuscript is an intelligible. And it is wriitten standart English.After correcting, the article is suitable for publication. Please see attached annotated PDF from Reviewer #2 Reviewer #3: The manuscript entitled ‘The association between diet and mental health and wellbeing in young adults within a biopsychosocial framework’ with the aim to study the relationship between plant-based diet and mental health among young adults. The manuscript can be further improved based on the comments below. Methods Since few amendments were done on DSQ, the information on whether the questionnaire was tested/piloted prior to the study to be stated. Statistical analyses and missing data Line 210, information on percentage/pattern of missing data to be stated and discussed. Results Line 226, some measurements require proper tool/inventory to measure such as perceived stress, stressful life events, sleep. Using one or two questions may not enough to capture the real condition. The type of data for the explanatory variables and how it was treated in the regression analysis to be clearly stated. A statement on statistical test assumptions fulfillment would be useful. Table 1, the number of missing data for individual variable to be displayed. Table 2, for component 2, the reason(s) for the two negative values to be explained. Table 3, total N to be stated. Title too short. Table 4, for item categories, the categories name to begin with capital letter. Table 5, B to be written as Unstandardized B. Line 281, for anxiety 65.1% but in Table 4 it showed 65.2%. Line 297 – 303, results to be presented in table form. Decimal point for percentages in the text in the results section to be standardized i.e. at least 1 decimal point. Discussion Line 401, for the sentence ‘relatively small sample size and the associated lack of power’ figures to be provided to support the statement. Not all references are conformed to the journal format. ****** 6. PLOS authors have the option to publish the peer review history of their article (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 Reviewer #3: 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.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. Attachments Attachment Submitted filename: PONE-D-20-39899_reviewer #2 de-identified.pdf https://doi.org/10.1371/journal.pone.0252358.r001
Revision 1
23 Apr 2021 Author Response The line numbers refer to the revised manuscript with TRACKED changes. Responses to Reviewer #1: n/a Responses to Reviewer #2: Reviewer submitted comments in manuscript PDF as follows: Line 57: The reviewer suggests to write ‘here’ instead of ‘herein’. We believe that ‘herein’ is the grammatically correct term to use in this case as we mean to say ‘in this text’ (see definition of ‘herein’: https://www.oxfordlearnersdictionaries.com/definition/english/herein) Line 145: The reviewer suggests to add ‘overall quality of life’ in addition to the abbreviation QoL. We would like to highlight that the definition for the abbreviation was already given in Line 80 (Introduction section) when the abbreviation is first mentioned in the text. This in accordance with the formatting guideline of the journal, see here: https://journals.plos.org/plosone/s/submission-guidelines Line 243: The reviewer suggests to write (n=339) after sentence. We are unclear about this suggestion since the number of participants is already clearly stated in said sentence: “The total sample consists of n=339 participants.” Do you mean for us to state the total number of participants again in that same sentence or elsewhere? Table 1 (Line 256): The reviewer notes that total count of observations for item ‘sexual orientation’ does not add up to n=339 and suggests we “correct all the tables”. Please note that, originally, we state in the footnote of the table, “n may vary due to missing data”. We did not impute missing data for these items. Therefore, for some variables, we have less than 339 observations. However, to respond appropriately to the reviewer’s concern and to make the tables more intuitive for the reader, we have added rows depicting the n of missing observations for each of the non-imputed items in Table 1. Table 4 (Line 289): The reviewer notes that percentages do not add up to 100%. This discrepancy happened due to rounding to one decimal. However, we have revised the tables and have rounded the decimals so that categories in tables now add up to 100%. We did find one typo which was corrected (see Table 4 QoL ordinal, Very good 4.7 instead of 4.1.). Responses to Reviewer #3: Methods Since few amendments were done on DSQ, the information on whether the questionnaire was tested/piloted prior to the study to be stated. We changed the following sentence in the Method section in Line 163: “The final version used in this study was not pilot-tested and had 28 items (see supplementary materials for questionnaire)”. We further added the following to the Discussion section in Line 430: “We further used a slightly amended version of the DSQ to make it more applicable to the local context. These amendments were minor and consisted of replacement of foods with limited relevance with those that were more relevant to the research question. We did not conduct a pilot study with this altered measure. However, the wording and structure of the questions were not altered, we therefore assume the potential bias due to issues of interpretability to be negligible.” Statistical analyses and missing data Line 211, information on percentage/pattern of missing data to be stated and discussed. We added the following to the revised manuscript (Line 204): “Overall, missingness was fairly low in this sample. More specifically, missingness was as follows for the variables included in the logistic regression models: Age: 4.4%; Gender: 2.1%; Ethnicity: 3.2%; Sleep: 2.1%; Physical activity: 2.9%; Stressful life events: 3.5%; Weight satisfaction: 0.9%; Social support: 0.1%. Due to the sensitivity of some of these items as well as a high prevalence of ‘prefer not to say’ responses among the missing observations, we could not assume a missing completely at random pattern. Therefore, complete case analysis would not have been appropriate. Instead, multiple imputation is suggested as best practice” [Sterne, J. A. C., White, I. R., Carlin, J. B., Spratt, M., Royston, P., Kenward, M. G., Wood, A. M., & Carpenter, J. R. (2009). Multiple imputation for missing data in epidemiological and clinical research: Potential and pitfalls. BMJ, 338(7713), 157-160. https://doi.org/10.1136/bmj.b2393]. Results Some measurements require proper tool/inventory to measure such as perceived stress, stressful life events, sleep. Using one or two questions may not enough to capture the real condition. We agree with the reviewer that some of the concepts used as covariables are complex and would indeed benefit from more extensive measurements. We decided to use single-item measures or more simple measures, respectively, for some of these concepts to keep respondent burden low. The questionnaire used in this study was already fairly long (since the measures for the outcome variable and the main explanatory variables were extensive) but we did not want to omit these important variables as their inclusion presents a significant advancement over previous studies in this area. To keep this trade-off as insignificant as possible, we exclusively used single-item measures that have been widely used and validated. Furthermore, it has been shown that single-item measures often suffice to measure concepts such as quality of life and others (Bowling, A. (2005). Just one question: If one question works, why ask several? Journal of Epidemiology and Community Health (1979), 59(5), 342-345. https://doi.org/10.1136/jech.2004.021204). The items on overall quality of life and on social support were taken from the Patient-Reported Outcomes Measurement Information System Scale version 1.2 (PROMIS®). The PROMIS® is a measure to assess patient-reported health outcomes and previous research has shown evidence for its reliability and precision in measuring health-related symptoms and functioning (Cella, D., Riley, W., Stone, A., Rothrock, N., Reeve, B., Yount, S., … Hays, R. (2010). The Patient-Reported Outcomes Measurement Information System (PROMIS) developed and tested its first wave of adult self-reported health outcome item banks: 2005–2008. Journal of Clinical Epidemiology, 63(11), 1179–1194. https://doi.org/10.1016/j.jclinepi.2010.04.011). Stressful life events were measured with the College Student’s Stressful Event Checklist. This checklist contains 32 items which had been modified from its original version for adults, the Social Readjustment Rating Scale to reflect appropriate events in the population of college students. Each item is assigned a specific value that corresponds to the potential stress magnitude of the event (Holmes, T. H., & Rahe, R. H. (1967). The social readjustment rating scale. Journal of Psychosomatic Research, 11(2), 213–218. https://doi.org/10.1016/0022-3999(67)90010-4). Values are summed up to calculate an overall score which reflects mild (total score <150), moderate (total score between 150 and 300) or severe stress (total score >300) due to these events. Despite its dated origin, this measure and its adapted versions continue to be among the most widely used and cited instruments to measure stressful life events and have been found to be a robust measure to identify events that may lead to stress-related outcomes (Scully, J. A., Tosi, H., & Banning, K. (2000). Life Event Checklists: revisiting the Social Readjustment Rating Scale after 30 years. Educational and Psychological Measurement, 60(6), 864–876. https://doi.org/10.1177/00131640021970952). Items on overall stress, physical activity, sleep, satisfaction with one’s weight (as a proxy for body image), and sociodemographic variables were adapted from the National College Health Assessment II (NCHA-II) of the American College Health Association. The NCHA-II is a survey that collects data on student health status and behaviours as well as factors influencing academic performance in order to provide universities with information on students’ health needs and previous research has shown evidence for adequate reliability and validity of the measure (American College Health Association. (2013). American College Health Association-National College Health Assessment II: reliability and validity analyses 2011. Hanover, MD: American College Health Association.). We added the following to the Discussion section (see Line 437): “Single-item measures for capturing covariates were chosen to reduce respondent burden. While these measures may not be as detailed as multi-dimensional measures, they have been shown to be useful when measuring aspects of respondents’ health.”; and we added this reference to the list: Bowling, A. (2005). Just one question: If one question works, why ask several? Journal of Epidemiology and Community Health (1979), 59(5), 342-345. https://doi.org/10.1136/jech.2004.021204 The type of data for the explanatory variables and how it was treated in the regression analysis to be clearly stated. We assume the reviewer refers to whether data was categorical or continuous? We added the following sentence in the Results section (see Line 295 -> beginning of results on models): “Explanatory variables age, sleep, physical activity, stress, stressful life events, weight satisfaction, social support, and PCA scores were entered in the model as continuous variables. Gender and ethnicity were entered as categorical variables.” If your comment refers to something else, please let us know and kindly clarify. A statement on statistical test assumptions fulfillment would be useful. The sentence “Assumptions for linear models were met” is already included in the manuscript, please see Line 231. We added the following details (see Line 232): “Assumptions were checked as follows: Independence of cases was given due to the study design (each observation exists only once, is not paired with an observation in another group nor is it influenced by another observation). Collinearity was assessed through VIF values (largest VIF should be <10; average VIF should not be substantially >1) and tolerance statistics (which should be >0.2; Field, 2013). Normality was assessed through the normal probability plots of the residuals. Homoscedasticity and linearity were checked through residuals vs. fitted plots.” Table 1, the number of missing data for individual variable to be displayed. Done, please see revised manuscript. Table 2, for component 2, the reason(s) for the two negative values to be explained. Principal Component Analysis (PCA) is based on correlations among variables. If variables in a component are positively correlated with each other, the loadings will be positive. If there are negative correlations, some of the loadings will be negative. In this example, you would expect that plant-based meat and dairy alternatives are inversely correlated with animal-based foods. We added the following sentences to the manuscript in Line 267: “Two items with cross-loadings were observed. The items on plant-based alternatives to meat and dairy milk had positive loadings on the first component (plant foods) and negative cross-loadings on the second component, which are the animal-based foods.” Table 3, total N to be stated. Title too short. Done, please see revised manuscript. Table 4, for item categories, the categories name to begin with capital letter. Done, please see revised manuscript. To make sure all tables are consistent, we made the same changes in Table 1. Table 5, B to be written as Unstandardized B. Done, please see revised manuscript. Line 281, for anxiety 65.1% but in Table 4 it showed 65.2%. Done, please see revised manuscript. Line 297 – 303, results to be presented in table form. The results described in this section refer to the unadjusted associations between the main explanatory variable and the outcomes of interest. These unadjusted correlations do not remain significant once confounding variables are taken into consideration. In this study, we particularly aimed to highlight the importance of consideration of confounding variables as unadjusted effects have been overrepresented in past studies. This is why we originally omitted presentation of the unadjusted correlations in table form. However, we now added this table, please see what is now Table 5. Decimal point for percentages in the text in the results section to be standardized, i.e. at least 1 decimal point. Done, please see revised manuscript. As is customary, we kept the 2 and 3 decimal points for the results of Beta and p-values, respectively. Discussion Line 401, for the sentence ‘relatively small sample size and associated lack of power’ figures to be provided to support the statement. We realize that this sentence was misleading. We rephrased to the following in Line 406: “The relatively small sample size and the potential lack of power…” and added this sentence in Line 408: “This could be mitigated in future studies with larger sample sizes.” Not all references are conformed to the journal format. We double-checked this before resubmission and hope to not have missed any errors. Attachments Attachment Submitted filename: PONE-D-20-39899_Response to Reviewers.docx https://doi.org/10.1371/journal.pone.0252358.r002
14 May 2021 Decision Letter - Sıdıka Bulduk, Editor The association between diet and mental health and wellbeing in young adults within a biopsychosocial framework PONE-D-20-39899R1 Dear Dr. Rossa-Roccor, 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 for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. 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, Sıdıka Bulduk, Prof. Dr. Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: https://doi.org/10.1371/journal.pone.0252358.r003
Formally Accepted
24 May 2021 Acceptance Letter - Sıdıka Bulduk, Editor PONE-D-20-39899R1 The association between diet and mental health and wellbeing in young adults within a biopsychosocial framework Dear Dr. Rossa-Roccor: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. 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. If we can help with anything else, please email us at plosone@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. Sıdıka Bulduk Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0252358.r004

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