Committee (5201951338311), and was performed in accordance with the ethics standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.Consent to participate: All participants provided written informed consent. Consent for publication:All participants provided consent for their responses to be included in aggregate in a peer-reviewed journal article. Availability of data and material: Data are available upon requestCode availability: All input files are available upon request Authors' contributions: Both authors contributed to the study conception and design. Data collection and analysis were performed by KF under the supervision of MKF. The first draft of the manuscript was written by KF, and MKF assisted in revising and preparing the manuscript for submission. Both authors read and approved the final manuscript.

The Diagnostic and Statistical Manual of Mental Disorders – Fifth Edition (DSM-5) features hundreds of diagnoses comprising a multitude of symptoms, and there is considerable repetition in the symptoms among diagnoses. This repetition undermines what we can learn from studying individual diagnostic constructs because it can obscure both disorder- and symptom-specific signals. However, these lost opportunities are currently veiled because symptom repetition in the DSM-5 has not been quantified. This descriptive study mapped the repetition among the 1,419 symptoms described in 202 diagnoses of adult psychopathology in Section II of the DSM-5. Over a million possible symptom comparisons needed to be conducted, for which we used both qualitative content coding and natural language processing. In total, we identified 628 distinct symptoms: 397 symptoms (63.2%) were unique to a single diagnosis, whereas 231 symptoms (36.8%) repeated across multiple diagnoses a total of 1022 times (median 3 times per symptom; range 2-22). Some chapters had more repetition than others: For example, every symptom of every diagnosis in the Bipolar and Related Disorders chapter was repeated in other chapters, but there was no repetition for any symptoms of any diagnoses in the Elimination Disorders, Gender Dysphoria, or Paraphilic Disorders. The most frequently repeated symptoms included insomnia, difficulty concentrating, and irritability—listed in 22, 17, and 16 diagnoses, respectively. Notably, the top 15 most frequently repeating diagnostic criteria were dominated by symptoms of major depressive disorder. Overall, our findings lay the foundation for a better understanding of the extent and potential consequences of symptom overlap.

Recent work on the empirical structure of psychopathology has aimed to address some limitations that can arise from traditional categorical classification approaches. This research has focused on modeling patterns of co-occurrence among traditional diagnoses, uncovering a variety of well-validated dimensions (or spectra) of psychopathology, spanning common and uncommon mental disorders. A model integrating these empirically derived spectra (the Hierarchical Taxonomy of Psychopathology; HiTOP) has been proposed. However, the placement of obsessive-compulsive disorder (OCD) within this model remains unclear, as studies have variably found OCD to fit best as part of the Fear, Distress or Thought Disorder spectra. One reason for this may be the heterogeneity of symptoms experienced by individuals with OCD, which is lost when analysing categorical diagnoses. For example, different symptom clusters within OCD—such as washing and contamination versus obsessions and checking—may be differentially associated with different spectra in the HiTOP model. The aim of this study was to test this hypothesis. Data were collected in an anonymous online survey from community participants with high levels of psychopathology (n = 609), and analyzed in a confirmatory factor analysis framework. The results indicated that the washing and contamination and symmetry and ordering symptom clusters fit best under the Fear spectrum, whereas the obsessions and checking and hoarding clusters fit best under the Thought Disorder spectrum. These findings suggest that OCD may be best characterized as cross-loading between the Fear and Thought Disorder spectra, and highlight the importance of accounting for diagnostic heterogeneity in future research.