PONE-D-21-02934

Association between life events and later depression in the population-based Heinz Nixdorf Recall study – the role of sex and optimism

PLOS ONE

Dear Dr. Gronewold,

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 plus one reviewer 

have read your manuscript. We feel that it addresses an interesting question but all sections of the manuscript need to be revised before it can be accepted. In particular the introduction does not provide a sufficient review of previous related research discussing the relationship between depression and life  event experiences. Additional relevant research needs to be described and evaluated in more depth. Reference is also made to the stress arising from the COVID pandemic yet this paper does not address the impact of COVID. This point needs to be made clear or reference to COVID deleted. There is also insufficient justification for examining age as a moderator. The introduction mentions a lack of research on gender effects but the discussion mentions research that addresses this issue. Material in the discussion should also be in the introduction to create a better rationale for the study. See the comments of reviewer one for specific examples. The methods section lacks detail on numerous places. It is not clear when the study took place or how the experience of life events was measured. In the results section the difference on SRRS  and CED scores could analysed for the different subgroups. There are a number of issues concerning the discussion. The stance on causality  between life events and depression is not clear either in introduction or the discussion, but was particularly problematic  The discussion of  related findings is not well-organized, making it difficult to understand why the studies are grouped together. Additional points have been raised by Reviewer1. In your revision address all points raised by Reviewer 1 and the points outlined in this letter.

Please submit your revised manuscript by January 27, 2022. 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.

Please include the following items when submitting your revised manuscript:

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If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

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,

Barbara Dritschel, PhD

Academic Editor

PLOS ONE

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2. We note that the grant information you provided in the ‘Funding Information’ and ‘Financial Disclosure’ sections do not match. 

When you resubmit, please ensure that you provide the correct grant numbers for the awards you received for your study in the ‘Funding Information’ section.

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In your revised cover letter, please address the following prompts:

a) If there are ethical or legal restrictions on sharing a de-identified data set, please explain them in detail (e.g., data contain potentially sensitive information, data are owned by a third-party organization, etc.) and who has imposed them (e.g., an ethics committee). Please also provide contact information for a data access committee, ethics committee, or other institutional body to which data requests may be sent.

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We will update your Data Availability statement on your behalf to reflect the information you provide.

4. One of the noted authors is a group or consortium Heinz Nixdorf Recall Study Investigative Group. In addition to naming the author group, please list the individual authors and affiliations within this group in the acknowledgments section of your manuscript. Please also indicate clearly a lead author for this group along with a contact email address.

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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: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

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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: No

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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

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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: This paper explored the association between the experience of important life events in the previous six months (measured using the Social Readjustment Rating Scale; SRRS) and depressive symptoms in a large population-based sample. In particular, the study examined whether sex and optimism moderated the association between life events and depression. The results showed that (1) people who had experienced important life events in the previous 6 months exhibited a greater number of depressive symptoms than people who had not experienced an important life event in the previous 6 months; (2) in those who had experienced an important life event, people with high SRRS scores exhibited a greater number of depressive symptoms than those with lower scores; (3) the association between SRRS score and depressive symptoms was stronger in women than men; and (4) the association between SRRS score and depressive symptoms was higher in pessimists than optimists. The authors concluded that women and pessimists should be targeted by prevention programmes to help them cope with stressful life events, and that specialized therapy may be required.

Comments/questions

1. The introduction opens with a reference to ongoing COVID pandemic as an example of an important, life-changing event (lines 47-48), which sets the study up as though it will measure the effect of the pandemic on depressive symptoms. However, it appears that the data for this study were in fact collected many years before the pandemic began. It would be good to make clearer in the introduction that this study is not about the pandemic specifically.

2. In general, the introduction does not describe the context for the study in enough detail. Information about previous studies that have examined the association between life events and depression is scarce (refs 5-9 on lines 59-62), giving the impression that there is relatively little existing research in this area. For example, the authors state that previous studies have not generally examined the effect of sex on this relationship (lines 78-80). However, in the discussion, two sex effects in previous studies are mentioned for the first time (lines 332-334 and lines 341-342), and several more details about these and other previous studies are presented. These details were needed in the introduction, to make it clear how the current study builds on previous work.

3. In lines 78-81 and line 90, age is mentioned as a potential moderating factor and a main focus of this study. However, although age was included in the models, it was not discussed in any detail.

4. In the method section the authors state that the data for this study were drawn from a previous study for which participants were recruited around 20 years ago, with follow-ups at 5 and 10 years (lines 94-98). It is not clear when the data for this study were actually collected – at the outset of the original study, in a follow-up examination, or across multiple time points?

5. It is not entirely clear what instructions participants were given for the self-administered questionnaire (lines 104-108). Were the examples of important life events on line 106 provided to participants as examples, or were the participants left to decide on their own what constituted an important life event (this seems to be what is implied by “open response format” on line 108/113-114)? If left to decide on their own, is it possible that women/men and optimists/pessimists used different criteria to determine what constituted an important life event?

6. On lines 112-115 the authors argue that their open response format offers more flexibility than using a checklist of life events, yet participants’ responses were evaluated according to a checklist of events for which normative data on severity were available. It is not clear why the open response format is therefore more flexible. Perhaps the authors could expand on this idea. To what extent were participants left to self-determine what constituted an important life event?

7. Was there a reason why all of the life events were evaluated by only one rater (lines 108-110)? How can the authors be sure that the rater’s evaluations were reliable? Given the flexible open-response format, did any participants report life events that were not on the existing checklist of events? If so, how were these responses dealt with?

8. Since the comparisons of interest in this study were women vs. men and optimists vs. pessimists, it would have been helpful to see some data on the SRRS scores and CES-D scores in these different subgroups. Were optimists and pessimists equally likely to report important life events, for example?

9. The argument is made that both positive and negative life events can be experienced as stressful due to the need to readjust (e.g., lines 72-73, lines 126-127). Following on from point 6 above, is it possible that, for example, optimists were more likely to report positive important life events, and this could explain the weaker relationship with depressive symptoms?

10. In the abstract, the authors state that they examine the presence of important life events and the RESULTING life event stress (line 26). Similarly, elsewhere the argument is made that higher stress is associated with higher depression scores (e.g., line 310-312). However, since the study did not directly measure stress, it is not clear that the participants in this study experienced stress, only that these life events tend to be stressful. These claims could be worded a little more carefully, to reflect what was actually measured.

11. The authors’ stance on the causality of the relationship between life events and depression was unclear. In lines 52-55 of the introduction, they state that a robust and causal association between stressful life events and depression has become established, whereby stressful life events trigger depression. Later, it is acknowledged that the current study is unable to draw conclusions about causality, and that the authors rely heavily on other studies to conclude that stressful life events cause depression (line 376). The arguments in the conclusion then appear to depend on the causality evidenced by other studies, rather than on the data presented in the current study. Given that this study is apparently the first to measure the moderating effects of sex and optimism, how can we be confident that this assumption of causality is justified?

12. In the discussion section, there is a list (beginning on line 315) of several previous studies that have explored similar research questions, albeit using different scales, sampling methods, etc. Some of the findings of these previous studies were consistent with the current findings, while others were inconsistent. The list format is quite repetitive, and it is difficult to follow the argument throughout – what is the overall message? The argument would be clearer if the findings from the previous studies could be aggregated in a meaningful way, such as by the methods used, the time period sampled, etc.

13. It is not clear why a less comprehensive assessment of life events using a checklist of 8 events vs. free response would potentially reverse the sex effect (lines 334-335). This argument needs to be made more explicit. The same applies to the potential difference between clinical and subclinical depression (lines 336-338).

14. On lines 356-363, there is a section on previous uses of SRRS (refs 11, 12, 13) showing that depressives had higher stress scores (i.e., more/more serious life events) than controls in 2/3 studies, and that stress score associated with depression severity in one study. This information would be better in the introduction (see point 2, above).

15. On lines 378-380, the authors argue that even if the causality is reversed, such that depression leads to the experience of stressful life events, “this still has important clinical implications in a way that the experience of life events must be considered more in the prevention and treatment of depression”. This argument was difficult to follow; if depression causes stressful life events, how could consideration of the experience of life events prevent or treat depression?

16. A new study is introduced in the conclusion on lines 389-396. It would be better to include this argument in the main body of the discussion so that the conclusion remains focused on the current investigation.

Minor points

Line 84-85 reads “From the clinical point of view, especially subclinical depression is important because it is associated with…”; it would read better as “From a clinical point of view, subclinical depression is especially important because….”

Lines 152-155 – this sentence is quite long, and would read better with commas.

Lines 310-311 – “In case important life events were experienced” would read better as “In participants who experienced important life events”

Line 311-312 – “higher stress… was again significantly associated…” – the “again” appears to be redundant here

Line 313 – “Women and individuals with pessimistic personality were more susceptible to the negative influence of life events on depression”. The wording is ambiguous, as it seems to suggest there is a negative association between life events and depression, rather than the positive association that was observed.

Line 317 – “The so far largest population-based study” would read better as “So far, the largest population-based study”

Line 350 – “this study could show….” presumably means “this study showed that….”?

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Reviewer #1: No

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PONE-D-21-02934R1Association between life events and later depression in the population-based Heinz Nixdorf Recall study – the role of sex and optimismPLOS ONE

Dear Dr. Gronewold

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. Both one reviewer and I have closely examined your revised manuscript. The main theoretical  point that needs be addressed is whether stronger association between life event stress and depression in the pessimist group is due to increased statistical power because the sample size is larger and therefore the impact this would have on your conclusions.  There  also needs to be more detail about the second rater coding and also the reliability calculations for the scoring of life events. A reference is needed  to support the argument that life events have more impact on men than women in line 392.   A few minor typographical/wording issues are  also outlined below in the comments of Reviewer 1. Please address all these points in your revision. 

 Please submit your revised manuscript by June 23, 2022. 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.

Please include the following items when submitting your revised manuscript:

• 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 you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

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,

Barbara Dritschel, PhD

Academic Editor

PLOS ONE

Journal Requirements:

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.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

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2. 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

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

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4. 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: No

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5. 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

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6. 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 authors have addressed the previous points that were raised, and the re-working of the introduction and discussion makes the message much clearer. The inclusion of the additional information in the supplementary tables is also very useful. I have one main question arising from the inclusion of these new tables:

- Table S4 shows the frequency of different life events stratified by optimism, and shows that the cut off for determining whether a participant is an optimist or a pessimist results in many more pessimists than optimists (i.e., 0.8% of the optimist group is 6 participants, but 0.8% of the pessimist group is 32 people). Is it possible that the stronger association between life event stress and depression in the pessimist group is due to increased statistical power because the sample size is larger? To put it another way, does the association look smaller in the optimist group because of lower power? If this is a possibility, how would it affect the conclusions?

Aside from that question, I have just a few minor comments after my second reading of the manuscript. In the following comments, line numbers refer to the line numbers in the revised manuscript.

1. line 70: "self-report screenings which are often not feasible in large population based studies" - I think the authors are arguing that self-report measures are usually used in larger studies because structured interviews are usually not feasible, but the wording makes it sound like it's the self-report measures that are not feasible.

2. lines 151-152: I think it would be good to include the details of the second-coding and reliability analysis for the life event scoring in here, so that readers can see that the scoring of life events was carried out more rigorously.

3. line 175: "optimism is regarded AS a stable trait" - the word as is missing

4. line 327: stronger influence of stress on optimists compared to pessimists - this appears to be the opposite of what is claimed elsewhere

5. line 392-393: an argument is made about some life events having more impact on men vs. women, and vice versa. A reference is needed here

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7. 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

[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.

Association between life events and later depression in the population-based Heinz Nixdorf Recall study – the role of sex and optimism

PONE-D-21-02934R2

Dear Dr. Gronewold,

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.

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Kind regards,

Barbara Dritschel, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments: