High Degree of Uncertainty New Study: Psychiatrists Agree on a Diagnosis in Only 55% of Cases

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Psychiatrists assessing the same written patient cases agreed on a diagnosis only 55% of the time in an international study. The findings highlight persistent differences in how clinicians interpret symptoms, raising questions about diagnostic consistency and its implications for patient care and research.

In the 1970s, psychiatric diagnoses were marked by considerable uncertainty and disagreement. Since then, organisations such as the American Psychiatric Association and the World Health Organization (WHO) have worked to develop standardised diagnostic criteria that psychiatrists around the world can use.

These efforts have shaped modern psychiatry by establishing common, criteria-based systems for diagnosing mental disorders across institutions and national borders.

However, a new study, led by researchers at the University of Copenhagen, suggests that major challenges remain. In the study, 1,038 psychiatrists and physicians working in psychiatry from 19 countries were presented with nine written patient case descriptions. Each participant was assigned two cases and asked to determine the most appropriate diagnosis.

The results surprised the researchers.

“Our study shows that when two psychiatrists diagnose the same patient, they will agree only 55% of the time. We consider that worryingly low. In fact, it is similar to the levels reported in some of the studies conducted in the 1970s, which prompted the development of standardised diagnostic criteria in the first place,” says Professor and Consultant Psychiatrist Julie Nordgaard.

“This is not about psychiatrists doing a poor job. Rather, it reflects the fact that, despite the existence of diagnostic systems, clinicians continue to differ in how they interpret symptoms and which features they consider most important. We need a greater degree of consensus, otherwise patients risk receiving changing diagnoses and treatments,” she adds.

Same Symptoms, Different Diagnoses

The study found substantial variation in diagnostic agreement across different mental disorders. Diagnoses within the schizophrenia spectrum proved particularly challenging.

“Cases that could be diagnosed either as schizophrenia or schizotypal disorder generated especially high levels of disagreement. In many of these cases, agreement among participants was well below 50%,” says PhD candidate Mateo Boberg, the study’s first author.

According to Boberg, one reason is that symptoms frequently overlap across psychiatric disorders. For example, obsessive thoughts may occur in both obsessive-compulsive disorder (OCD) and schizophrenia.

“These are not random errors. There is a clear pattern to the disagreements. This likely reflects the fact that diagnostic categories are not as clearly defined as we have assumed, when experienced psychiatrists can interpret the same symptom presentations so differently.”

Diagnostic Uncertainty Undermines Research

Disagreement about diagnoses is an obvious concern for patients. But the researchers argue that diagnostic uncertainty also threatens the reliability of some kinds of psychiatric research¸ explains Professor Mads Gram Henriksen:

“In research, it is essential that we know exactly what we are studying. If a considerable part of participants enrolled in a study on treatment of personality disorders actually suffer from schizophrenia, the study’s results become difficult to interpret. Which condition is the treatment having - or not having - an effect on? Personality disorders or schizophrenia?”

The researchers argue that progress in psychiatric research risks remaining limited until there is a clearer and more widely shared understanding of what mental disorders are and how they can be distinguished from one another. Greater diagnostic agreement, they say, is a prerequisite for the breakthroughs needed to improve patient care.

“WHO’s ICD-10 diagnostic system, which participants in the study used to assess the cases, contains more than 200 diagnoses, a complexity that may contribute to uncertainty. At the same time, many psychiatric conditions are inherently multifaceted,” says Julie Nordgaard and concludes:

“In our view, it is necessary to take a step back and develop more precise descriptions of psychiatric disorders so that clinicians can distinguish them more clearly. It may also be necessary to reduce the number of diagnostic categories.”

The study, Reliability of Psychiatric Diagnoses in the 21st Century, has been published in Frontiers in Psychiatry.

Original Article: Reliability of psychiatric diagnoses in the 21st century; Frontiers in Psychiatry; DOI:10.3389/fpsyt.2026.1891625

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