ICD-11 vs DSM-5: which system should be used in Poland?

Two classification systems - where did they come from?

In mental health, two widely used classification systems operate in parallel. The first is the ICD, the International Classification of Diseases, maintained by the World Health Organization. It covers not only mental disorders, but the whole of medicine: infectious diseases, cancers, cardiovascular diseases, injuries, causes of death, mental disorders, neurodevelopmental disorders and many other areas of health. The newest revision is ICD-11.^[4]

The second system is DSM, the Diagnostic and Statistical Manual of Mental Disorders. DSM is prepared by the American Psychiatric Association. Its current fifth edition is DSM-5, and the text revision is DSM-5-TR. Unlike ICD, DSM does not cover the whole of medicine, but focuses on mental disorders.

Both systems were created to provide a shared diagnostic language. They allow clinicians, researchers and institutions to describe similar states in a more comparable way. They differ, however, in the responsible institution, scope, construction of criteria and administrative function.

For the patient, differences between ICD-11 and DSM-5 are usually not the most important issue. Anxiety, depressed mood, intrusive thoughts or psychotic symptoms remain the same experience regardless of which system is used to describe them. What matters most is the quality of the diagnostic process: interview, differential diagnosis, assessment of functioning and selection of help.

ICD-11 - a global, general medical classification

The most important feature of ICD-11 is its global and general medical character. ICD-11 is not a psychiatric manual only. It covers the whole of medicine, while mental, behavioural and neurodevelopmental disorders are one chapter within it. This means ICD codes can be used in medical documentation, health statistics, reporting, epidemiological analyses and health information systems.

WHO has also prepared the CDDR, Clinical Descriptions and Diagnostic Requirements for ICD-11 Mental, Behavioural and Neurodevelopmental Disorders. This manual describes mental, behavioural and neurodevelopmental disorders in ICD-11. WHO presents the CDDR as a comprehensive manual supporting accurate and reliable identification and diagnosis of these disorders in clinical settings worldwide.

The CDDR is not a simple list of codes. For each disorder it describes the clinical picture, essential features, boundaries with other entities, course, development, cultural, age and sex-related differences and differential diagnosis. This matters because ICD-11 is not meant only for entering a code in documentation, but also for a more organised understanding of the clinical picture.

ICD also has a system-level function. It is the ICD classification that forms the basis for documentation and health statistics in many countries. In Poland too, the formal point of reference for documentation, reporting and billing is ICD, not DSM.

DSM-5 - a manual focused on psychiatry

DSM-5 is narrower in scope because it concerns only mental disorders. It was prepared by the American Psychiatric Association and is especially deeply rooted in clinical, research and educational practice in the United States.

DSM-5 traditionally uses more operational diagnostic criteria. They are often written as lists of symptoms with defined numerical and time thresholds. This way of describing disorders can be very useful in research, because it allows investigators to define more precisely who meets criteria for a given study group.

DSM-5 does not replace ICD in its administrative function. Even where DSM is widely used clinically or scientifically, reporting and statistical systems usually require reference to ICD codes. ICD and DSM are therefore not simple competitors. They often function in parallel: DSM as a psychiatric and research manual, ICD as a classification system for the whole of medicine and the basis for reporting.

Where do ICD-11 and DSM-5 converge?

ICD-11 and DSM-5 describe largely the same field of mental disorders. Both systems include depressive disorders, bipolar disorders, anxiety disorders, schizophrenia and other psychotic disorders, obsessive-compulsive disorders, eating disorders, disorders due to substance use and neurodevelopmental disorders.

This convergence is not accidental. Work on DSM-5 and ICD-11 partly took place during a similar period, and one goal was to reduce unnecessary discrepancies where possible. As a result, many disorders are described similarly, even if details of criteria, terminology or chapter organisation differ between systems.

Both systems also include similar general principles: distinguishing disorder from normal variation, assessing the impact of symptoms on functioning, differential diagnosis and excluding other causes. In practice, a clinician familiar with one system can usually find their way around the other, although they should not assume that categories are identical one to one.

A study comparing ICD-11 and DSM-5 diagnostic requirements for 103 shared entities found that some categories are essentially similar, some have minor differences and some differ substantially in definition or organisation.

Where do ICD-11 and DSM-5 differ?

The most visible difference concerns the construction of criteria. DSM-5 more often uses detailed symptom lists and numerical thresholds. ICD-11 in many places uses more flexible essential features and clinical descriptions intended to be useful across different health care systems, including outside highly specialised centres.

Differences also concern the organisation of selected groups of disorders. The clearest example is personality disorders. ICD-11 moves away from former personality types as the main categories and introduces a model based on severity, trait domains and an optional borderline pattern. DSM-5 in its main section still retains traditional categorical personality disorder types, while placing a dimensional model in an alternative section. This is one of the most important differences between the systems.

Differences also appear in stress-related disorders. ICD-11 separates PTSD (6B40) and complex PTSD/CPTSD (6B41) as distinct categories. DSM-5 does not introduce CPTSD as a separate diagnosis in this way. Both systems include prolonged grief disorder, but differ in details, especially the time criterion and symptom structure.

There are also differences in gaming-related disorders. ICD-11 introduces gaming disorder as a diagnosis within disorders due to addictive behaviours, whereas DSM-5 treated internet gaming disorder as a condition requiring further study rather than a full category in the main classification. WHO officially includes this category in ICD-11 as part of the global classification system.

Which system applies in Poland?

In the Polish health care system, the formal point of reference is ICD, not DSM. ICD is used in medical documentation, health statistics, reporting and billing. Therefore, in formal practice in Poland, diagnoses should be recorded in the ICD system.

It is important to distinguish ICD as a formal system from the specific revision used at a given moment in national systems. ICD-11 is the newest WHO revision and has been in force as an international classification since 1 January 2022, but full implementation of ICD-11 in Poland requires adaptation of IT systems, regulations, procedures, forms, reporting and training. The Ministry of Health indicates that Poland has an approximately five-year period to implement ICD-11 and adapt it to the national system.

The e-Health Centre is involved in the 'ICD-11 stage II' project, whose aim is to support implementation of ICD-11 in the Polish health care system. The project includes increasing knowledge about ICD-11, preparing code sets for legal acts, including ICD-11 codes in death reporting and improving the quality of the Polish version of the classification.

DSM-5 is not an official system in Poland. It may, however, be used as a supporting tool: in science, research, training, comparative work and reading international literature. It should not replace ICD in formal medical documentation kept within the Polish health care system.

Transition from ICD-10 to ICD-11 - what changes?

For Polish clinical practice, the comparison of ICD-11 with ICD-10 is often more important than the comparison of ICD-11 with DSM-5. Transition from ICD-10 to ICD-11 is not merely a change in code numbering. It changes the structure, language and way many disorders are described.

ICD-11 introduces new categories, reorganises parts of chapters and changes the description of some groups of disorders. For example, personality disorders are described by severity and trait domains rather than by a list of former types. Schizophrenia is no longer divided into classical subtypes. Autism is described as a spectrum with specification of intellectual and language functioning. Separate categories also appear, such as complex PTSD, prolonged grief disorder and gaming disorder. These changes fit the wider ICD-11 architecture, which WHO provides as a digital classification with a Browser, Coding Tool and API.

For clinicians, this means learning the new logic of the classification. For patients, the change usually does not mean a sudden change in the problem itself, but it may mean a more precise description of difficulties. For example, someone who previously received an unclear or mixed diagnosis may in ICD-11 be described through a more functional symptom profile, severity level or additional qualifiers.

How does the classification system affect the patient?

From the patient's perspective, the choice of classification system usually matters less than the quality of the diagnostic process. Symptoms, suffering and needs remain the same regardless of whether a specialist refers to ICD-11, ICD-10, DSM-5 or DSM-5-TR.

What truly affects the quality of help is a reliable assessment: a detailed interview, determining symptom duration, differential diagnosis, assessment of functioning, recognition of co-occurrence and attention to the patient's life context. A classification system is a tool, not the diagnosis itself.

The record in documentation does have formal significance. In Poland, medical documentation and reporting are based on the ICD system. A diagnosis recorded with an ICD code is therefore readable to other specialists and consistent with the requirements of the health care system.

If a patient encounters a diagnosis described according to DSM-5, this does not necessarily mean a contradiction. Often it is the same or a very similar condition described in another system. If in doubt, it is worth asking the specialist what the ICD equivalent would be and whether differences between the systems matter in the specific case.

Which system should be chosen in study and practice?

For students, psychologists, psychiatrists and people learning diagnostics in Poland, the basic point of reference should be ICD, because it has formal relevance in health care. In the context of current knowledge, familiarity with ICD-11 and the CDDR - the official clinical descriptions and diagnostic requirements for mental, behavioural and neurodevelopmental disorders - is especially important. WHO published the CDDR as a manual supporting clinical diagnosis of these disorders.

Knowledge of DSM-5 remains very useful. Many scientific publications, especially from the United States, use DSM criteria. For someone reading scientific literature, writing academic papers or analysing international research, the ability to compare ICD and DSM is a major advantage.

In clinical practice in Poland, DSM-5 can be treated as a supporting tool, but not as a formal replacement for ICD. The safest approach is: ICD for documentation and system compliance, DSM as an additional point of reference in study, research and comparison of literature.

Summary - ICD as the formal standard, DSM as a complement

ICD-11 and DSM-5 are two mature systems for describing mental disorders. They share a common goal: organising diagnoses and creating a language understandable to clinicians and researchers. They differ, however, in scope, responsible institution, administrative function and construction of criteria.

In Poland, the formal reference system is ICD. DSM-5 is not an official system, but it may be used as a supporting tool in study, research and training. ICD-11 is the newest revision of the WHO classification, but its full implementation in Poland is a process requiring organisational, legal and IT changes. The Ministry of Health and the e-Health Centre are carrying out activities related to this implementation.

The most important conclusion is simple: the quality of care is not determined by the name of the system, but by the reliability of the diagnosis. Classifications are tools. Diagnosis requires interview, differential diagnosis, assessment of functioning and clinical responsibility.

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