Implications of the Symptom-Level Overlap Among DSM Diagnoses for Dimensions of Psychopathology

Research on the patterns of covariation among mental disorders has proliferated, as summarized in the Hierarchical Taxonomy of Psychopathology (HiTOP). This brief letter sought to examine whether symptom overlap represents an important source of bias in the statistical structure of psychopathology. I found that 358 pairs of the DSM-5 diagnoses covered by the HiTOP framework had one or more overlapping, and that a third (n = 130; 34%) of the unique constituent symptoms do reinforce the higher-order structure of HiTOP through repetition within dimensions and/or between dimensions in the same superspectrum. By contrast, 86% of the possible pairs of diagnoses did not have any shared symptoms, and the majority of the unique constituent symptoms (n = 222; 58%) do not influence the structure through repetition; a fifth (n = 71; 19%) work against the HiTOP structure at the subfactor, spectrum, and superspectrum level. I conclude that symptom-level homogeneity likely inflates the similarity and consequent covariation of some DSM diagnoses—e.g., in the Antisocial Behavior dimension—and research on the statistical structure of psychopathology should account for this potential source of bias. However, the patterns of symptom overlap in the DSM are not strong enough to make the HiTOP structure a foregone conclusion.