Review Reports - The Hierarchical Taxonomy of Psychopathology in Adolescents: Support for a Neurodevelopmental Spectrum Without ADHD

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors This manuscript addresses an important and timely topic regarding the hierarchical structure of psychopathology in adolescents and the placement of neurodevelopmental disorders within the HiTOP framework. The inclusion of both community and clinic-referred samples strengthens the study, and the use of confirmatory factor analysis to evaluate competing structural models is a notable strength. The findings contribute meaningfully to ongoing discussions regarding the dimensional classification of psychopathology and the role of ADHD within the HiTOP model. The manuscript is generally well structured, and the statistical analyses are appropriate for the stated aims. The inclusion of multiple neurodevelopmental disorders beyond ADHD represents an important contribution to the literature, particularly given the relative lack of adolescent-focused HiTOP studies. However, several areas require clarification and improvement prior to publication. Major Comments

Language and Writing Quality
The manuscript would benefit from careful English language editing throughout. There are multiple grammatical issues, typographical errors, awkward sentence constructions, and formatting inconsistencies that reduce readability. Examples include repeated wording, punctuation errors, inconsistent terminology, and occasional unclear phrasing. Some sections of the discussion and introduction are overly long and repetitive.
Overstatement of Conclusions
The conclusion that ADHD “belongs” within the externalizing spectrum rather than the neurodevelopmental spectrum may be somewhat overstated given the modelling limitations and the non-admissible cross-loading solution. The findings support stronger statistical association with the externalizing factor in the tested models, but this does not necessarily invalidate its neurodevelopmental classification within DSM-5-TR. The discussion should acknowledge this distinction more cautiously.
Externalizing Factor Reliability
The omega reliability coefficient for the externalizing factor in the community sample was relatively low (.46), which raises concerns regarding factor stability and interpretation. Although the authors acknowledge this issue, the implications should be discussed in greater depth, particularly regarding the robustness of conclusions involving ADHD and ODD/CD placement.
Use of Binary Screening Variables
The analyses are based on dichotomized positive screening outcomes rather than dimensional symptom severity scores. This potentially reduces variability and may influence factor structure estimation. The authors should provide stronger justification for using binary indicators instead of continuous symptom scores derived from the CAPP-PRF.
Community Sample Characteristics
The prevalence rates reported in the community sample appear unusually high for several disorders, particularly specific learning disorder, depressive disorder, and conduct/oppositional problems. Additional discussion is needed regarding:

representativeness of the sample,
possible self-selection bias,
and interpretation of “positive screening” versus clinical diagnosis.

Concurrent Validity Section
The concurrent validity findings are somewhat limited and should be interpreted more cautiously. The correlations are generally small-to-moderate, and concurrent validity was only examined in the clinic-referred sample. This limitation should be more explicitly acknowledged.

Minor Comments

Several references are very recent and appropriate; however, some classic HiTOP references could be streamlined to reduce redundancy.
The introduction could be shortened slightly, particularly sections describing the original HiTOP model in extensive detail.
There are occasional formatting inconsistencies in abbreviations and terminology (e.g., “eternalizing” instead of “externalizing”; punctuation spacing; inconsistent capitalization).
Please carefully proofread tables for formatting consistency and alignment.
The supplementary materials are useful and appropriate.

Comments on the Quality of English Language

The manuscript is generally understandable and scientifically readable; however, the quality of English language could be improved throughout to enhance clarity, readability and precision. Several sections contain grammatical issues, awkward sentence construction, repetition and inconsistent terminology. Careful proofreading and professional language editing are recommended prior to publication.

Author Response

Dear Editor and Reviewers,

We thank the Editor and both Reviewers for the constructive and detailed feedback on our manuscript. The comments have substantially improved the rigor and clarity of the work. In the revised manuscript all changes are visible as tracked changes; below we respond to each comment point-by-point and indicate the corresponding location of the change in the revised manuscript. For ease of cross-referencing, reviewer comments are reproduced in italics in the left column.

On behalf of all authors,

Prof Rapson Gomez (corresponding author for revisions)

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study addresses the core controversial issue of the existence of a neurodevelopmental spectrum within the Hierarchical Taxonomy of Psychopathology (HiTOP) model and the classification of ADHD, conducting rigorous confirmatory factor analysis in two independent adolescent samples: a community sample and a clinic-referred sample. The research question holds significant theoretical and clinical importance. The methodological design is sound, and cross-validation with two samples enhances the reliability of the results. The core findings have implications for the refinement of the HiTOP model and the revision of the DSM-5-TR classification system. However, the manuscript has numerous issues requiring revision in terms of methodological rigor, standardization of results presentation, depth of discussion, and analysis of limitations.

Several key methodological issues require priority revision. First, there are concerns regarding sample bias and representativeness. The community sample was recruited from a paid online screening platform, introducing significant self-selection bias, and lacks key demographic information. The clinic-referred sample was entirely obtained from a single clinic in Perth, Australia, with referrals concentrated on ADHD, SLD, ASD, and intellectual assessments, resulting in severe referral filter bias. Males were significantly overrepresented in both samples, despite well-documented gender differences in the prevalence and presentation of mental disorders. Second, there are issues with measurement tools and variable operationalization. Converting the continuous symptom scores of the CAPP-PRF into binary "positive/negative screen" outcomes as observed variables resulted in substantial loss of information regarding symptom severity. ODD and CD were combined into a single variable due to the small number of positive ODD cases, which may obscure their distinct relationships with other disorders and is a major contributor to the low reliability of the externalizing factor. Additionally, only four neurodevelopmental disorders were included, excluding core types such as intellectual disability, tic disorders, and developmental coordination disorder. Finally, there are statistical analysis issues. The Omega coefficient for the externalizing factor was only 0.467 in the community sample and 0.687 in the clinic-referred sample, both below the acceptable threshold of 0.70. This is a critical issue affecting the validity of the study's conclusions and requires explicit reporting and in-depth analysis of the underlying causes. The modified three-factor model in the community sample had a TLI of 0.885 and an RMSEA of 0.076, which are at the upper limit of the acceptable range and should not be interpreted as "good fit". The unexpected finding that the internalizing factor correlated more strongly with anger and disruptive behavior than with anxiety in the clinical sample requires explanation. Furthermore, the manuscript does not mention the handling of missing data, which needs to be supplemented.

Results presentation requires comprehensive revision. There are numerous formatting errors and content omissions in the tables. Tables 2 and 4 are poorly formatted, with many loadings not aligned to the correct factor columns. Table 4 completely lacks factor loadings for Language Disorder and Speech Sound Disorder. Both tables incorrectly repeat "Specific Learning Disorder" where "Separation Anxiety Disorder" should appear. Supplementary Tables S1 and S2 are missing frequencies and percentages for the three subtypes of Specific Learning Disorder. Tables 1 and 3 are not formatted according to MDPI journal requirements, and all tables need to be recreated. Results description is also insufficiently clear and detailed. While it is noted that all factor correlations are below 0.80, meeting discriminant validity criteria, the magnitude and significance of these correlations are not explained—for example, the correlation between internalizing and externalizing factors reached 0.722 in the community sample. Concurrent validity results only report the direction and significance of correlations, without explaining the clinical and theoretical implications of the effect sizes.

The discussion and conclusion sections require further elaboration. There is overinterpretation of results: the claim that the findings support the robustness of the HiTOP model across the entire lifespan should be revised to state that the results are consistent with previous studies in child and adult samples, providing further evidence for the applicability of the HiTOP model across different age groups. The explanation for the classification of ADHD is insufficiently detailed and should expand on the consistency between core ADHD symptoms and the defining features of externalizing disorders, as well as the differences from core neurodevelopmental disorder characteristics. Integration with existing literature is inadequate: the manuscript does not sufficiently compare its findings with recent adolescent HiTOP studies such as Forbes et al. (2025) and Hankin et al. (2026), nor does it adequately discuss the implications of the results for the DSM-5-TR and ICD-11 classification systems. The discussion of limitations is superficial: only a list of limitations is provided without explaining their specific impact on the results or proposing clear future research directions. The limitations of the cross-sectional design also need to be added. Clinical implications are underdeveloped, with only general references to "precision diagnosis" without specific applications to clinical practice.

Several minor issues and details also require revision. These include multiple spelling and grammatical errors: for example, "Smple" in the title of Supplementary Table S3 should be corrected to "Sample", and "eternalizing" should be changed to "externalizing" throughout the text. References 34 and 36 are identical, so the duplicate entry should be removed, and all references should be checked for compliance with MDPI journal formatting requirements. For Supplementary Figure S1, it is recommended to add the full names of disorders within each box or clarify abbreviations more clearly in the figure legend to improve readability.