PONE-D-21-32224Childhood trauma and schizotypy in non-clinical samples: 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: Yes

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

Reviewer #1: Yes

Reviewer #2: 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: 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

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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: The primary aim of this review paper is to present the association between psychometric schizotypy (i.e., schizotypal traits in non-clinical samples) and early life adversities. The manuscript is well-written, provides quantitative summaries of available literature according to current best practices, and results are clearly presented. The topic is important and contributes to an area that is thus far under researched. Recommendations are made to improve presentation of the data extraction process and interpretation of the results and some minor recommendations are also offered:

1. Introduction: The introduction is well-written and nicely reviews the rationale/existing support for childhood adverse experiences as risk factors for psychosis-like experiences (PLEs) and schizotypy. Given this is a review of correlational observations, what evidence exists, if any, for schizotypy or PLEs to be considered risk factors for experiencing adverse childhood experiences or for increasing the likelihood of experiencing more adverse childhood experiences. For example, is there longitudinal research that establishes PLEs or schizotypy (may be difficult because typically understood as a diagnosis in adulthood) preceding adverse childhood events?

2. Introduction: How is “childhood adverse event” defined, any events prior to age 18? Please clarify.

3. Method: Many steps of the methods are clearly described in detail which is important for replication. One additional clarification How were articles screened at the title, abstract, and full-text level? Did two independent reviewers screen all articles at all levels of review (i.e., title, abstract, and full-text level) and resolve discrepancies? Was double-screening completed at just at an abstract or full-text level, please clarify lines 148-149 (“screening and eligibility assessment…).

4. Method: Since the study was not preregistered (which the authors discuss in the introduction), it would be helpful to have more information about structure of coding, training of coders, and a priori protocols put in place prior to data extraction. For example, how were coders trained? Were there ongoing consensus meetings, did multiple coders extract data from a same group of articles and discuss discrepancies before completing all extraction? Was there a manual or other documentation of coding decisions/definition of categories made available? The same question would be helpful to address for the screening process, did all coders independently screen all potential articles and then resolve discrepancies or was there a smaller subset of screening done and then some type of reconciliation that happened to make sure coders were employing similar inclusion criteria? Relatedly, were there categories that were coded for (e.g., race/ethnicity) that were not included in the final analyses due to insufficient data? It is common to see meta-analyses discuss categories that were planned but not able to be included due to insufficient study reporting. This can be an important future direction to discuss in the manuscript (e.g., if only 5% of studies reported on participant race and ethnicity, the authors can provide citable statements to this effect and recommend that future studies of psychometric schizotypy include this information).

5. Method: please provide more detailed information regarding how “general population sample” was defined. The authors specify that no clinical psychosis or personality disorder could be present but do not specify if study participants could have other mental health diagnoses. If participants could have other mental health diagnoses (e.g., depression) or be part of a treatment-involved sample (e.g., outpatient clinic participants) it would be helpful to have this information included in Table 3 of study characteristics (e.g., inclusion of mental health diagnoses Y/N). If study participants were relatives of individuals with schizotypy or psychosis or otherwise identified as high-risk for schizotypy, were the included in this meta-analysis? If yes, it would be helpful to present this as well in Table 3.

a. If family history was reported in studies at a sufficient rate, a recommendation is made to include family history as a predictor of effect size as well.

6. Results: If possible, a recommendation is made to present the country (or perhaps reduce by broader area/continent) for each study in Table 3 and to include country as a predictor of effect sizes in the analyses.

7. Discussion: If possible, a strong recommendation is made to review included articles for reporting on race. If studies report race of study participants at an acceptable level (e.g., even being able to dichotomize % white, although no ideal), it would be important to enter race as a predictor of effect size. A recommendation is made to include a discussion of how race impacts adverse childhood experiences and the relationship to PLEs/schizotypy. There is a growing body of work on how race impacts this relationship and may be important to better understand the findings of this study (e.g., Anglin et al., 2014; Gibson et al., 2016)

a. References:

i. Anglin DM, Lighty Q, Greenspoon M, Ellman LM. Racial discrimination is associated with distressing subthreshold positive psychotic symptoms among US urban ethnic minority young adults. Soc Psychiatry Psychiatr Epidemiol. 2014 Oct;49(10):1545-55. doi: 10.1007/s00127-014-0870-8. Epub 2014 Apr 3. PMID: 24695907.

ii. Gibson, L. E., Alloy, L. B., & Ellman, L. M. (2016). Trauma and the psychosis spectrum: A review of symptom specificity and explanatory mechanisms. Clinical Psychology Review, 49, 92-105.

Minor points:

- Abstract: lines 22-23, edit suggested “By contrast, no systematic review or meta-analysis has…”

- Some statistical reporting is inconsistent (e.g., italicizing all rs relating to effect size throughout).

- Use gender/sex consistently throughout manuscript with fidelity to how these were assessed by study to adhere to language free of bias. For example, lines 461-462 (“Turning to gender, the physical abuse-schizotypy link was larger in samples containing more female participants”). Use of sex (e.g., male, female) is recommended when referring to sex assigned at birth while gender refers to a social construct/identify (e.g., man, woman). If assessing/analyzing sex, a recommendation is made to define as “sex assigned at birth” and then use “male/female” throughout the manuscript rather than conflate sex and gender terms (e.g., https://apastyle.apa.org/style-grammar-guidelines/bias-free-language/gender).

Reviewer #2: The current study assessed whether early life adversities are associated with schizotypal personality traits in the non-clinical population. The authors conducted a systematic review and meta-analysis of associations between early life adversities schizotypal traits in non- clinical samples. Twenty-six studies (N=15,818 participants) were included in the review. Meta-analyses showed that all forms of abuse (emotional, physical and sexual) and neglect (emotional and physical) were significantly associated with schizotypy. The association of schizotypy traits with emotional abuse (r = .33: 95%CI .30 to .37) was significantly larger than for all other form of abuse or neglect. The current study found a dose-response relationship between all forms of abuse/neglect and schizotypy scores in non-clinical samples with the stronger association being for emotional abuse.

The manuscript addressed an interesting question regarding early childhood abuse and its relationship to personality traits related to schizophrenia spectrum disorders in a nonclinical sample using metanalysis. Given that early abuse is often associated with psychosis, this research is of interest to those who study resiliency. Some clarifications are needed to make the article more readable.

Introduction

• Page 5, line 72: Provide examples of schizotypal traits.

Results

• Page 10, line 190:Why were studies that scored below 8 included?

• Page 41: please explain the Trim and fill analysis method.

Discussion

• Page 51: “On quality assessment, fewer than half of the studies were rated as being methodologically robust” This should be included in your weaknesses section.

• Page 5, line 79: “Adversities in early life are common, with approximately 40% of the general adult population reporting at least one type of adverse experience (e.g. parental mental illness, domestic violence, physical, emotional, and sexual abuse, neglect) before the age of 18;” Can you check ACE scale to see what other adverse experiences might be applied? Maybe include parental substance abuse or parents in jail as factors.

• Page 6-7, ending at line 119: Unsure of what the numbers 1 and 2 mean here; are there any combinations of these search terms in 1 and then in 2?

• Page 7, line 137: “The review followed PRISMA guidelines, however, it was not pre-registered;” Please summarize the PRISMA guidelines

• Page 8, line 143: “. . . (c) include a measure of childhood trauma before the age of 18 years (excluding peer victimization; i.e., bullying; to assess for trauma where the perpetrator is an adult;” Peer victimization/bullying was included on page 6 though

• Page 11, line 202: “The mean age of participants across the 26 studies was 27.06 with a standard deviation of 12.21 (age range 18-95); median = 25;” Why only assess such a young population? Please acknowledge this as a limitation in the discussion

• Page 11, line 216: “The CATS, CECA and ACE-Q assess all aforementioned types of adversity as well as other adversities, such as parental conflict and control;” Be more specific such as parental mental illness, substance abuse, family member going to prison

• Page 17, lines 277-279: “. . . found that physical abuse showed links with an array of schizotypal traits only in women, that emotional abuse associated with an array of schizotypal traits in both sexes and that sexual abuse did not have a link with schizotypy” Should be in an earlier paragraph

• Page 39, Table 4: Specify are these positive and negative affects? Or something else?

o Put “Child” before each type of abuse

o “Neglect” should be split into both Physical Neglect and Emotional Neglect separately

• Page 39, lines 314-316: “Emotional abuse invariably correlated with the negative dimension and with total schizotypy scores; Neglect (physical and emotional) with the disorganized dimension; and finally, total trauma scores with the dositive dimension scores;” What are negative, disorganized, and positive dimensions? Please specify

• Page 38, line 320: Specify these measures as emotional abuse, physical abuse, and sexual abuse

• Page 40, line 330: “Heterogeneity and variance among effect sizes of studies were assessed using the q statistic and the I2 statistic;” Some explanation of Q statistics and I2 statistics will be helpful

• Page 41, Table 5: Specify each measure as Child Emotional Abuse, Child Physical Abuse, Child Sexual Abuse, Child Emotional Neglect, and Child Physical Neglect.

• Page 42, lines 355-359: “. . . the effect size for (child) emotional trauma is in the medium range; while all other trauma types (physical abuse, sexual abuse, physical neglect and emotional neglect) (in childhood) were in the small effect size range. This suggests that while all types of abuse and neglect are associated with schizotypy, (childhood) emotional abuse is more strongly associated; and was significantly more strongly associated with schizotypy scores than any other (childhood) trauma or neglect;” Specify these traumas and abuse as occurring in childhood

• Page 43, line 379: “We also looked at a multiple regression model including both age and gender as predictors and the results did not change;” What are the outcome variables? What other predictors are there?

• Page 43, line 380: “Gender continued to moderate the impact of physical abuse on schizotypy, while age was ns;” Provide more detailed explanation on how moderation was established.

• Page 48, line 497: “The most consistent being reported for (childhood) emotional abuse and the domain of negative schizotypal traits and total schizotypy . . .” Add childhood to specify emotional abuse.

• Page 48, lines 498-502: “for physical/emotional neglect and the disorganized domain; and for total trauma scores with the positive domain. It is notable that early sexual trauma had little evidence of associations with any specific schizotypy domains but did show links with total schizotypy;” This information is really important but hard to understand. Please refresh readers on what disorganized and positive domains mean.

• Pages 48-49, lines 507-508: “. . . all types of traumas (sexual, physical, and emotional abuse, and neglect) . . .” Are these all childhood variables? If so, please specify.

• Page 51, line 558: “Finally, as with psychosis, the links between early life trauma and schizotypy are undoubtedly complex and possible confounding factors cannot be eliminated;” Please acknowledge that the sample is very young (mean age = 26)

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Reviewer #1: No

Reviewer #2: Yes: Weili Lu

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Childhood trauma and schizotypy in non-clinical samples: a systematic review and meta-analysis

PONE-D-21-32224R1

Dear Dr. Toutountzidis,

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,

Sarah Hope Lincoln

Academic Editor

PLOS ONE

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: All previous comments have been addressed by the authorship team. I have no additional comments/concerns for the authorship team.

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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

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