Diagnosing and Classifying Psychological Disorders
A first step in the study of psychological disorders is carefully and systematically discerning significant signs and symptoms. How do mental health professionals ascertain whether or not a person’s inner states and behaviors truly represent a psychological disorder? Arriving at a proper diagnosis—that is, appropriately identifying and labeling a set of defined symptoms—is absolutely crucial. This process enables professionals to use a common language with others in the field and aids in communication about the disorder with the patient, colleagues and the public. Two common classification manuals help professionals to diagnose mental disorders—the DSM and the ICD.
The Diagnostic and Statistical Manual of Mental Disorders (DSM-5)
Although a number of classification systems have been developed over time, the one that is used by most mental health professionals in the United States is the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), published by the American Psychiatric Association (2013). (Note that the American Psychiatric Association differs from the American Psychological Association; both are abbreviated APA.)
Additions and revisions were made in March 2022, so the most current edition is called the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR). This text includes the updates from the DSM-5-TR, though in most instances, we continue to reference the diagnostic manual simply as the DSM-5.
What the DSM includes
The first edition of the DSM, published in 1952, classified psychological disorders according to a format developed by the U.S. Army during World War II (Clegg, 2012). The DSM-5 includes many categories of disorders (e.g., anxiety disorders, depressive disorders, and dissociative disorders). Each disorder is described in detail, including:
- an overview of the disorder (diagnostic features),
- specific symptoms required for diagnosis (diagnostic criteria),
- what percent of the population is thought to be afflicted with the disorder (prevalence information), and
- risk factors associated with the disorder.
Figure 1 shows lifetime prevalence rates—the percentage of people in a population who develop a disorder in their lifetime—of various psychological disorders among U.S. adults. These data were based on a national sample of 9,282 U.S. residents (National Comorbidity Survey, 2007).
| DSM Disorder | Total | Females | Males |
|---|---|---|---|
| Major Depressive Disorder | 17% | 20% | 13% |
| Alcohol Abuse | 13% | 7% | 20% |
| Specific Phobia | 13% | 16% | 8% |
| Social Anxiety Disorder | 12% | 13% | 11% |
| Drug Abuse | 8% | 5% | 12% |
| Post-traumatic Stress Disorder | 7% | 10% | 3% |
| Generalized Anxiety Disorder | 6% | 7% | 4% |
| Panic Disorder | 5% | 6% | 3% |
| Obsessive Compulsive Disorder | 3% | 3% | 2% |
| Persistent Depressive Disorder | 3% | 3% | 2% |
More recent data shows that the most prevalent disorders at any given time (not over a lifetime) are anxiety disorders, as shown in the following chart.[1]
comorbidity
The DSM also discusses comorbidity, meaning the co-occurrence of two or more disorders in the same person. Comorbidity is common in mental health, and it has real consequences for treatment planning and outcomes.
For example, substance use disorders (SUDs) frequently co-occur with other mental disorders, including anxiety and depression. This overlap can complicate diagnosis because symptoms may be caused by:
- the mental disorder itself,
- substance use or intoxication,
- withdrawal, or
- a combination of these factors.
For this reason, clinicians often need to assess symptoms over time and consider whether they persist when substance use has stopped (when safe and clinically appropriate).
Comorbidity is not limited to substance use. Depressive and anxiety disorders also commonly co-occur, and the presence of one often increases the likelihood of symptoms of the other.
Changes to the DSM Over Time
The DSM has changed considerably since its original publication in 1952. First published as a 130-page manual with 106 diagnoses, it has grown substantially. The DSM-III (1980) introduced explicit diagnostic criteria and included 265 diagnoses across 886 pages. Interestingly, the current DSM-5 contains 237 disorders—fewer than the 297 in DSM-IV—though the manual itself is longer due to more extensive descriptions.
Perhaps the most significant example of evolving diagnostic thinking involves homosexuality. The first two editions listed homosexuality as a disorder. Following activism, scientific debate, and research showing homosexuality to be a normal variation of human sexuality, the APA voted in December 1973 to remove it. A compromise diagnosis, “ego-dystonic homosexuality” (for individuals distressed by their homosexual orientation who desired to change), remained in DSM-III but was removed in 1987. The World Health Organization removed homosexuality from its International Classification of Diseases in 1990. This history illustrates how diagnostic categories are shaped by both scientific evidence and evolving social understanding.
A major innovation with DSM-5 (2013) was adopting an iterative revision process, allowing ongoing updates rather than waiting for completely new editions. The DSM-5-TR (Text Revision), published in March 2022, reflects this approach. Key changes include adding prolonged grief disorder as a new diagnosis, clarifying criteria for more than 70 disorders, adding codes for suicidal behavior and nonsuicidal self-injury, updating terminology to use gender-affirming language, and enhancing cultural considerations including attention to how racism and discrimination may affect diagnosis.
Some critics argue that expanding psychiatric diagnosis may overpathologize normal human experiences. The finding that nearly half of all Americans will meet criteria for a DSM disorder at some point fuels this concern. For example, DSM-5 removed the “bereavement exclusion” that had prevented diagnosing major depression within two months of losing a loved one—meaning grief can now potentially meet criteria for depression. Supporters argue this ensures treatment for severe symptoms regardless of trigger; critics worry it pathologizes normal grief. These debates highlight an ongoing tension between the need for reliable diagnoses and the risk of medicalizing normal human variation.
Other Diagnostic Tools—The International Classification of Diseases
International Classification of Diseases
While the DSM-5-TR is the primary diagnostic guide in the United States, other classification systems exist. The International Classification of Diseases (ICD), published by the World Health Organization, is used more widely in Europe and globally. The ICD-11, released in 2022, includes mental, behavioral, and neurodevelopmental disorders in Chapter 6. Many countries use both systems, and ongoing efforts aim to harmonize the two classification approaches.
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 this module is based on the DSM paradigm.
- Hannah Ritchie and Max Roser (2018) - "Mental Health". Published online at OurWorldInData.org. Retrieved from: 'https://ourworldindata.org/mental-health' [Online Resource] ↵