International Classification of Diseases

 Learning Objectives

  • Explain how the International Classification of Diseases is used to classify mental disorders

International Classification of Diseases

A blue and white map of the continents.

Figure 1. The ICD is used globally while the DSM is rarely used outside of the United States.

A second classification system, the International Classification of Diseases (ICD), is also widely recognized. Published by the World Health Organization (WHO), the ICD was developed in Europe shortly after World War II and, like the DSM, has been revised several times. The ICD is much larger and more comprehensive than the DSM because it deals with all manners of healthcare and is not specific only to mental health. The categories of psychological disorders in both the DSM and ICD are similar, as are the criteria for specific disorders; however, some differences exist. Although the ICD is used for clinical purposes, this tool is also used to examine the general health of populations and to monitor the prevalence of diseases and other health problems internationally (WHO, 2013). The ICD-11, in development for many years but officially adopted in January 2022, is the eleventh revision and replaced the ICD-10 as the global standard for coding health information and causes of death. The ICD-11 has not yet been officially implemented in the United States, so until at least 2025, clinicians still use the ICD-10-CM.


The following mental disorders have been newly added to the ICD-11, but were already included in the American ICD-10-CM adaption: binge eating disorder, Bipolar II disorder, body dysmorphic disorder, excoriation disorder, frotteuristic disorder, hoarding disorder, and intermittent explosive disorder.

The following mental disorders have been newly added to the ICD-11, and are not in the ICD-10-CM: avoidant/restrictive food intake disorder, body integrity dysphoria, catatonia, complex post-traumatic stress disorder, gaming disorder (generally defined as the problematic, compulsive use of video games that results in significant impairment to an individual’s ability to function in various life domains over a prolonged period of time), olfactory reference disorder (a psychiatric condition in which there is a persistent false belief and preoccupation with the idea of emitting abnormal body odors which the patient thinks are foul and offensive to other individuals), and prolonged grief disorder.

Other notable changes include the following:

  • Distinct personality disorders have been collapsed into a single personality disorder diagnosis, using a dimensional (as opposed to categorical) model. Personality disorders are classified as mild, moderate, or severe.
  • All subtypes of schizophrenia (e.g., paranoid, hebephrenic, catatonic) have been removed. Instead, a dimensional model is used with the category symptomatic manifestations of primary psychotic disorders, which allows the coding for positive symptoms, negative symptoms, depressive symptoms, manic symptoms, psychomotor symptoms, and cognitive symptoms.
  • Persistent mood disorders, including cyclothymia and dysthymia, have been deleted.
  • The ICD-10 differentiated between phobic anxiety disorders, such as agoraphobia, and other anxiety disorders, such as generalized anxiety disorder. The ICD-11 merges both groups together as anxiety or fear-related disorders.
  • All pervasive developmental disorders are merged into one category, autism spectrum disorder, except for Rett syndrome, which is moved to the developmental anomalies chapter.
  • Hyperkinetic disorder is renamed attention deficit hyperactivity disorder, and a distinction in subtypes is made between predominantly inattentive, predominantly hyperactive-impulsive, and combined. Hyperkinetic conduct disorder has been removed.
  • Acute stress reaction has been moved out of the mental disorder chapter, and placed in the chapter “Factors influencing health status or contact with health services.” Thus, in the ICD-11, acute stress reaction is no longer considered a mental disorder.

The ICD-11 features five new chapters. Those most relevant to mental disorders are the new chapters on “Sleep-Wake Disorders” and “Conditions Related to Sexual Health.”

ICD chapters

Below is a list of all chapters of the ICD-11. You can view the ICD-11 here or learn more about it in this ICD-11 reference guide.

  1.  Certain Infectious or Parasitic Diseases
  2.  Neoplasms
  3.  Diseases of the Blood or Blood-Forming Organs
  4.  Diseases of the Immune System
  5.  Endocrine, Nutritional or Metabolic Diseases
  6. Mental, Behavioral, or Neurodevelopmental Disorders
  7. Sleep-Wake Disorders
  8.  Diseases of the Nervous System
  9. Diseases of the Visual System
  10. Diseases of the Ear or Mastoid Process
  11. Diseases of the Circulatory System
  12. Diseases of the Respiratory System
  13. Diseases of the Digestive System
  14. Diseases of the Skin
  1. Diseases of the Musculoskeletal System or Connective Tissue
  2. Diseases of the Genitourinary System
  3. Conditions Related to Sexual Health
  4. Pregnancy, Childbirth, or the Puerperium
  5. Certain Conditions Originating in the Perinatal Period
  6. Developmental Anomalies
  7. Symptoms, Signs, or Clinical Findings Not Elsewhere Classified
  8. Injury, Poisoning or Certain Other Consequences of External Causes
  9. External Causes of Morbidity or Mortality
  10. Factors Influencing Health Status or Contact with Health Services
  11.  Codes for Special Purposes
  12. Supplementary Chapter Traditional Medicine Conditions—Module I
  13. Supplementary Section for Functioning Assessment
  14. Extension Codes

A study that compared the use of the two classification systems found that worldwide the ICD is more frequently used for clinical diagnosis, whereas the DSM is more valued for research (Mezzich, 2002). Most research findings concerning the etiology and treatment of psychological disorders are based on criteria set forth in the DSM (Oltmanns & Castonguay, 2013). The DSM also includes more explicit disorder criteria, along with an extensive and helpful explanatory text (Regier et al., 2012). The DSM is the classification system of choice among U.S. mental health professionals, and the modules in this course are based on the DSM paradigm.

Try It

Compassionate View of Psychological Disorders

A couple sitting on a couch. One is comforting the other.

Figure 2. It’s important to be considerate of those dealing with psychological disorders.

As these disorders are outlined, please bear two things in mind. First, remember that psychological disorders represent extremes of inner experience and behavior. If, while reading about these disorders, you feel that these descriptions begin to personally characterize you, do not worry—this moment of enlightenment probably means nothing more than you are normal. Each of us experiences episodes of sadness, anxiety, and preoccupation with certain thoughts—times when we do not quite feel ourselves. These episodes should not be considered problematic unless the accompanying thoughts and behaviors become extreme and have a disruptive effect on one’s life.

Second, understand that people with psychological disorders are far more than just embodiments of their disorders. We do not use terms such as schizophrenics, depressives, or phobics because they are labels that objectify people who suffer from these conditions, thus promoting biased and disparaging assumptions about them. It is important to remember that a psychological disorder is not what a person is; it is something that a person has—through no fault of their own. As is the case with cancer or diabetes, those with psychological disorders suffer debilitating, often painful conditions that are not of their own choosing. These individuals deserve to be viewed and treated with compassion, understanding, and dignity.

Watch It

Watch this CrashCourse Psychology video to better understand the history of diagnosing psychological disorders and how they are classified.

You can view the transcript for “Psychological Disorders: Crash Course Psychology #28” here (opens in new window).

Try It


axis: a category of information regarding one dimension of an individual’s functioning

categorical approach: attempts to categorize mental disorders into distinct diagnoses

dimension: refers to a continuum on which an individual can have various levels of a characteristic

dimensional approach: focuses on varying levels of different behaviors that a person exhibits, rather than whether or not a person meets criteria for a particular disorder.

gaming disorder: problematic, compulsive use of video games that results in significant impairment to an individual’s ability to function in various life domains over a prolonged period of time

International Classification of Diseases (ICD): authoritative index of mental and physical diseases, including infectious diseases, and the criteria for their diagnosis; published by the World Health Organization (WHO)

olfactory reference disorder: a psychiatric condition in which there is a persistent false belief and preoccupation with the idea of emitting abnormal body odors that the patient thinks are foul and offensive to other individuals