NEW HAVEN, CT — Using common diagnostic criteria might have limited generalizability to the large group of individuals with a low-probability symptom combination, according to a new study.
In the DSM and ICD, mental disorders are defined as polytheistic-categorical concepts. This means that a specific mental disorder is defined by multiple symptoms, but not all of them need to be present for a diagnosis, according to the report in JAMA Psychiatry.1
That allows for heterogeneity of symptoms among individuals with the same disorder, according to the authors, who point out: “In empirical research, most combinations were not found or only rarely found, prompting criticism of this heterogeneity.”
The study led by the Yale School of Medicine in New Haven, CT, and the VA Connecticut Healthcare System in West Haven sought to elaborate how symptom-based definitions and assessments contribute to a distinct probability pattern for the occurrence of symptom combinations.
The cross-sectional study involved a theoretical argument, simulation and secondary data analysis of 4 preexisting datasets, each consisting of symptoms from 1 of the following syndromes: post-traumatic stress disorder, depression, schizophrenia and anxiety. The researchers obtained from a variety of sources, including the National Institute of Mental Health Data Archive and the VA. With individual studies from 3,930 to 63,742 participants included, a total of 155,474 participants were analyzed between July 2021 and January 2024.
For each participant, the study team determined the presence or absence of each assessed symptom and their combinations. In addition, the researchers assessed the number of all combinations and their individual frequencies. The goal was to determine the probability or frequency of unique symptom combinations and their distribution.
Participants’ mean (SD) age was 47.5 (14.8) years; 33,933 (21.8%) self-identified as female and 121,541 (78.2%) as male.
“Because of the interrelation between symptoms, some symptom combinations were significantly more likely than others,” the authors pointed out. “The distribution of the combinations’ probability was heavily skewed, with most combinations having a very low probability. Across all 4 empirical samples, the 1% most common combinations were prevalent in a total of 33.1% to 78.6% of the corresponding sample. At the same time, many combinations (ranging from 41.7% to 99.8%) were reported by less than 1% of the sample.”
The study found that within-disorder symptom heterogeneity followed a specific pattern, consisting of few prevalent, prototypical combinations and numerous combinations with a very low probability of occurrence.
“Future discussions about the revision of diagnostic criteria should take this specific pattern into account by focusing not only on the absolute number of symptom combinations but also on their individual and cumulative probabilities,” the authors suggested. “Findings from clinical populations using common diagnostic criteria may have limited generalizability to the large group of individuals with a low-probability symptom combination.”
- Spiller TR, Duek O, Helmer M, Murray JD, et. Fielstein E, Pietrzak RH, von Känel R, Harpaz-Rotem I. Unveiling the Structure in Mental Disorder Presentations. JAMA Psychiatry. 2024 Aug 7:e242047. doi: 10.1001/jamapsychiatry.2024.2047. Epub ahead of print. Erratum in: JAMA Psychiatry. 2024 Sep 25. doi: 10.1001/jamapsychiatry.2024.3166. PMID: 39110437; PMCID: PMC11307158.
