PONE-D-23-00344Evidence on the links between water insecurity, inadequate sanitation and mental health: a systematic review and meta-analysisPLOS ONE

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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: Yes

Reviewer #2: Partly

Reviewer #3: Yes

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

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: 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: Yes

Reviewer #2: No

Reviewer #3: Yes

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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

Reviewer #2: Yes

Reviewer #3: 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: I think this is an important paper and one that needs to be published. I have only a couple areas that I feel need to be improved.

1.) The figures are very pixilated (low resolution) and difficult to read. It would be helpful if these could be redone in high resolution.

2.) Since the database search July 2022 till now (Feb 2023), there have been a few more papers published on this topic including at least one authored by Ian Ross (https://scholar.google.com/citations?user=gHAjfvcAAAAJ&hl=en). I know that a date must be chosen at some point but it would seem a good idea to update the search maybe up to the beginning of 2023.

Reviewer #2: This is a reasonably useful review on an important topic. It does have some important weaknesses, but they can be fixed. Some of the remedies I suggest may be unappealing, but would turn an OK paper into a great paper that will attract 5x more cites.

Six major comments:

1. Search strategy omits water supply

The authors have been fairly rigorous on their approach to the outcome (mental health) but unfortunately a bit weak on the exposures. The authors imply at the bottom of p.5 that they are building on Bisung and Elliot’s 2017 scoping review to make it systematic. However, for water terms, the authors search only for “(water insecurit* OR water scarcit*)”. I think the authors need to clarify how they are defining “water insecurity”, and whether inadequate access to water supply (using their sanitation terminology) is part of that, or only self-perceived water security (like HWISE and similar). Without this definition, it is unclear whether an ostensibly water supply oriented paper would be included or not. For example, if a piped water intervention study included mental wellbeing as an outcome, should that be included in this review even if a psychometric measure of water insecurity was not included (i.e. the exposure comparison would be two levels of water *service*).

Bisung & Elliot’s water search terms were “‘water supply’ or ‘water *security’ or ‘water access’ or ‘access to water’ or ‘water distribution*’ or ‘water availabilit*’ or ‘water quan*” which represent a more rounded and comprehensive search strategy. By focusing on only two search terms, and apparently a narrow definition of water insecurity, the authors have almost certainly missed relevant literature. The authors have mostly treated sanitation as a service (e.g. inadequate/poor sanitation) but not treated water in conceptually the same way. Their sanitation terms are “(inadequate sanitation OR sanitation insecurit* OR poor sanitation OR open defecation)”. Even then, these sanitation terms are far from ideal – why not just “sanitation”? this has undoubtedly resulted in excluded studies (see below).

Recommendation: authors re-run searches including more appropriate search terms for water supply and sanitation, de-duplicate, and include any additional studies identified. I understand that this may be unappealing. An alternative could be to keep the same results as now, but (i) justify in methods why water supply terms were not included; (ii) acknowledge the lack of water supply terms in the discussion as a substantial limitation; (iii) clearly define water security and why inadequate water supply is not part of it. I leave it to the editor to decide what to insist on. If the authors re-run searches they could also include the “missing” papers I note below. The authors might note that they only got 1599 EMBASE hits for their specific water search terms, but an order of magnitude for having used then “/water supply” subject header, a redeeming feature of an apparently flawed search strategy. But why include it is a subject term if not as a search term?

2. Missing papers

This paper (https://journals.plos.org/globalpublichealth/article?id=10.1371/journal.pgph.0000056)

was published in January ’22 and the searches were to July ‘22, so should have been picked up since it meets the inclusion criteria. It is unclear why it was not. This is evidence of the weak search strategy. I think it’s the first sanitation intervention study to include mental wellbeing outcomes.

This paper was published in October ’22 so after the searches, but the authors should mention it in discussion as (I think?) the only other example of an evaluation of a sanitation intervention which measured a mental wellbeing outcome.

https://bmjopen.bmj.com/content/12/10/e062517

I don’t know the water supply/security literature as well but my impression is that, given the weak search strategy, and the fact that the Freeman paper was missed, probably relevant water papers have been missed as well.

Here’s a water one from Oct ’22 https://www.sciencedirect.com/science/article/abs/pii/S1438463922001420

This supports the idea of clarifying the definitions and search strategy, re-running the searches, and updating the paper. I expect 5-10 additional papers would be included.

3. Engaging with what studies controlled for

Most meta-analyses focus on intervention studies. That way, depending on the quality of causal inference, you can be reasonably confident that the intervention caused a change in the outcome. All but one of the studies are not intervention studies. That makes it doubly-important to engage with what the studies controlled for. Otherwise everything is likely confounded with poverty in one way or another. Poorer people are more likely to be anxious/depressed etc., and poor people are more likely to be water insecure. Hey presto, water insecurity and depression are correlated! But it’s only if you adjust for poverty/wealth etc. that you’ll see the true effect size. This issue was not properly engaged with in this paper. The authors have “confounding” as an item in study quality (fig 2) but it’s not clear at all how this is defined/measured – see below on this. Table 3 or Table 4 really needs to engage with the confounding/adjustment issue. And I would also recommend conducting a sensitivity analysis excluding studies which did not control for confounders properly. Overall I think the pooled effect sizes are likely to be overestimated for this reason.

4. lack of relevant sensitivity analyses

Only looking at SGA by income group is not enough. Study quality is evaluated but the results are not used. The results of that exercise should be used to calculate an overall score per study, then include a sensitivity analysis in which only studies above X score (or excluding the bottom 2 quintiles for quality) are included, to see if results are being biased by a few low-quality studies. Otherwise what’s the point of reviewing study quality? Likewise ideally a SA on studies that did/didn’t adjust for clustering properly.

5. Study quality appraisal

An annex is needed which explains how each item in the EPHPP tool was defined. Were these the Qs used? https://www.ephpp.ca/PDF/Quality%20Assessment%20Tool_2010_2.pdf Just add the Qs to an annex, so it’s transparent, alongside how answers were converted into the red/yellow/green in figure 2. This is basic replication stuff. All systematic reviews should be replicable. As far as I can tell, this EPHPP study quality tool doesn’t evaluate whether studies adjusted for clustering. Studies which don’t do this, and there are many in WASH (Wolf 2022 explain - https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(22)00937-0/fulltext) will have underestimated standard errors and therefore 95% CIs. The authors need to flag this as a limitation.

6. Open science

Authors should put their meta-analysis datasets and analytical code underlying their results on a public repository like OSF.io. This should just be a given nowadays. Everything should be replicable, and what’s more it is PLOS policy - https://journals.plos.org/plosone/s/data-availability . The authors state “All relevant data are within the manuscript and its supporting information files” but that is not really true. Publish the actual dataset you analyse for the meta-analysis.

Other points

Abstract

- recommend the authors review PRISMA 2020 for abstracts, because their abstract is missing many several of the items. The PRISMA website is down, but here it is elsewhere https://journals.plos.org/plosntds/article/file?type=supplementary&id=10.1371/journal.pntd.0010822.s002

Introduction and methods

- p5 line L13 – also re sanitation there is disgust at seeing/smelling faeces which can trigger anxiety/shame. https://www.sciencedirect.com/science/article/pii/S0277953621000411

- p.6 3 lines from bottom (please use line numbers!)– clarify to “mental well-being” if that is what was searched for because wellbeing is a far broader concept. You haven’t included studies of water security and happiness for example. https://link.springer.com/article/10.1007/s10902-018-0060-6

- I’m assuming the DerSimonian and Laird random effects model was used. Best just to state that as there are alternatives which are more and more popular.

Results

- Shiras et al 2018 is really a qualitative study as it’s based on semi-structured IDIs – it should probably be excluded. But it’s up to the authors if they think those IDIs are providing quant data, because it is borderline.

- Table 4 on the whole is v useful. However, it needs to note p-values (ideally, but 95% CI OK as well) at all times when an association is claimed. It also needs to explain how water insecurity (or whatever the exposure is) was defined in each study. This should be in a supp mat table if no space. I would wager they are sufficiently different that the meta-analyses are comparing apples and pears, but that’s a discussion for another day.

- For the Stevenson 2016 study, the authors say “We did not find evidence of impact of the intervention on women’s psychological distress. Water insecurity was, however, predictive of psychological distress (p <0.01), independent of household food security and the quality of the previous year’s harvest.” So table 4 is slightly misleading re: this being an intervention study. The authors are using the observational result rather than the intervention result (which was no effect). And this is the ONLY study which was an intervention study! Needs to be clarified in table 4 and discussion (we need more intervention studies which measure these outcomes).

- For the SMD results and meta-analysis, it’s not clear what is being compared (difference between what and what?). this could be addressed in either table 3 or table 4 (or in a supp mat table)

Discussion

- Needs to more clearly state that there are no intervention studies! In order to allocate resources, we need to understand the relative impact of water interventions on water security. This paper goes into how using HWISE or similar can help inform resource allocation https://www.sciencedirect.com/science/article/pii/S0043135422012726

- Talk about water supply interventions, need to justify focus on water security as an exposure, when really it’s an intermediary outcome of water supply. the food security points are not that relevant. Need more attention on the above points and the limitations.

- the conclusion needs to be clearer that most of these studies are only measuring associations and have a weak claim on causal inference. Cf. issues with poverty confounding above. Suggest “we provide some evidence of an association between X and Y”

Reviewer #3: This is a well-written and important contribution to the literature surrounding water/sanitation access and health indicators. The analysis is thorough and careful, and the authors are indeed filling a gap in the academic literature. In my opinion, this paper will be a welcome contribution to PLOS ONE with the following suggested edits:

- On page 10, the authors note "Review Manager (RevMan) software was used for the meta-analysis. A random effects statistical model for meta-analysis was used..". The methodology should be explained in more detail here - explaining how the software gleans insight from the information provided to it. More detail would include why a random effects model was used.

- On the same page, more detail should be provided on how a forest plot provides insight into publication bias. In other words, the methodology needs to be laid out for the reader.

- Figures 1 and 2 have fonts that are difficult to read - they may need to be re-created. Figures 9-11 require that the axes labels be spelled out (rather than the use of acronyms only).

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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Evidence on the links between water insecurity, inadequate sanitation and mental health: a systematic review and meta-analysis

PONE-D-23-00344R1

Dear Dr. Kimutai,

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.

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Additional Editor Comments (optional):

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: All comments have been addressed

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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: Yes

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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: In my opinion the authors have adequately responded to the reviewer comments. I believe this manuscript is ready for publication.

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Reviewer #1: No

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