Mental disorders like depression and anxiety have many symptoms. However, people with the same diagnosis can show different combinations of those symptoms. Some experts worry that the symptom definitions are too broad.
However, a new Yale study found that most possible symptom combinations are rarely seen in real life. This suggests that broad criteria may be acceptable for diagnoses, but studies should consider symptom combinations. The study was published on August 7 in JAMA Psychiatry.
The third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM), published in 1980, started defining and diagnosing mental disorders. This manual is now in its fifth edition and is still widely used.
The goal was to make diagnoses more reliable. For example, if two patients with the same symptoms saw different doctors, they would get the same diagnosis, which was only sometimes valid.
The DSM system links multiple symptoms to each mental disorder, and patients need to have certain symptoms or a specific number of symptoms to be diagnosed.
The researchers tested their idea by creating a fake mental disorder with five symptoms. A patient must have at least two of these symptoms to get a diagnosis. They simulated 500 patients and repeated this 100 times.
They found that out of 32 possible symptom combinations, some were very common, but most were rare.
This pattern was also seen in real-life data for disorders like PTSD, depression, schizophrenia, and anxiety. Most symptom combinations were rare, and less than 10% of the possible combinations were standard.
In the PTSD data, 99.8% of possible symptom combinations were seen in less than 1% of people. In comparison, the most common 1% of combinations were found in 46.2% of people.
Spiller noted that while the DSM includes many symptom combinations, only a few are likely. Hence, the variety isn’t a problem.
However, this could affect research. Duek warned that findings from specialized clinics, which may see less common cases, might only apply to some of the population. This could also explain why some study results can’t be repeated.
The study shows that symptom variability isn’t random—it has structure and predictability, giving clinicians a more transparent framework.
Journal reference:
- Tobias R. Spiller, Duek, et al., Unveiling the Structure in Mental Disorder Presentations. JAMA Psychiatry. DOI: 10.1001/jamapsychiatry.2024.2047.