According to the World Health Organization, a mental disorder is a condition that involves disturbances in thinking, emotional regulation, or behavior. There are many different types of mental disorders, and around one in eight people around the world are impacted by some sort of mental disorder. While many effective prevention and treatment options exist, most people worldwide do not have access to effective care (World Health Organization, 2022).

Mental disorders can affect how we relate to others and make choices. Mental disorders, including mental illnesses, developmental disorders, substance use disorders, and other conditions, affect a range of people in every walk of life. These disorders may be more or less common; they may involve a single episode or recurrence; and they may be mild or more serious. However, receiving a formal diagnosis generally requires some impairment, or a reduction in a person’s ability to function, as a result of the disorder.

A smaller subset of mental disorders may be categorized based on a relatively more severe impairment. For example, serious mental illness is usually defined as someone over 18 having (within the past year) a diagnosable mental, behavior, or emotional disorder that causes serious functional impairment that substantially interferes with or limits one or more major life activities (SAMHSA, 2023). Disorders such as schizophrenia and bipolar disorder would generally be categorized as serious and persistent mental illness.

2.2.1 Diagnostic and Statistical Manual of Mental Disorders

The Diagnostic and Statistical Manual of Mental Disorders (DSM) is a classification system for mental disorders that is used in the United States by most mental health professionals. The DSM includes categories of disorders, with individual disorders in each category described in detail with diagnostic criteria and the percentage of the population that is diagnosed with each disorder. The first edition of the DSM was published in 1952, and it has undergone numerous revisions and updates, indicated by the Roman numerals that follow the title. The most recent text revision, in 2022, resulted in the American Psychiatric Association’s (APA) publication of the DSM-5-TR (figure 2.2). Information from the 2022 version is used in this text.

Figure 2.2 shows the cover of the latest version of the DSM: the DSM-5-TR.

Each edition of the DSM that is published brings substantial change to the understanding and management of mental disorders. For example, every new DSM edition has an increased number of disorders from the previous edition. Other substantial changes relate to societal norms and updated research. For instance, “homosexuality” was listed as a disorder in the original DSM and it was not until 1986 that it was fully removed from the DSM. Now, there is no disorder in the DSM that can be diagnosed based on sexual orientation.

Another notable evolution in the DSM, for purposes of this text, was the expansion of guidelines for diagnosing post-traumatic stress disorder (PTSD). Previously, PTSD was only diagnosable in people, primarily men, who served in the military. By the time the DSM-III was published, however, professionals had observed many similarities between impacted members of the military and people, primarily women, who had experienced trauma in the form of sexual assault. These populations had experienced different forms of trauma, but members of the military and sexual assault survivors were experiencing similar symptoms, and both met criteria for PTSD. This expansion gave voice and clinical recognition to survivors of events such as sexual assault and abuse by recognizing that PTSD can impact people outside of experiencing a universal traumatic event. We’ll discuss PTSD in its current diagnostic form later in the chapter.

2.2.2 Licenses and Attributions

“What Are Mental Disorders” by Kendra Harding is licensed under CC BY 4.0.

“What are Mental Disorders” is adapted from Mental Health and Substance Use Disorders by SAMHSA, which is in the Public Domain. Modification: Used some paragraphs verbatim and reworded others for clarity and consistency.

“Mental Disorders in the Criminal Justice System” by _______ is a remix of Psychology 2e, “15.1 What Are Psychological Disorders” and “15.2 Diagnosing and Classifying Psychological Disorders” by R. M. Spielman, W. J. Jenkins & M.D. Lovett, which is licensed under CC BY 4.0. Access for free at https://openstax.org/books/psychology-2e/pages/1-introduction. Modification: Used some paragraphs verbatim and reworded others for clarity and consistency.

Figure 2.2 “The DSM-5-TR” by American Psychiatric Association is in the Public Domain