Section Learning Objectives

• Explain what it means to make a clinical diagnosis.
• Define syndrome.
• Identify the two most used classification systems.
• Outline the history of the DSM.
• Identify and explain the elements of diagnosis.
• Outline the major disorder categories of the DSM-5.
• Describe the ICD-11

3.2.1. Clinical Diagnosis and Classification Systems

Before beginning any type of treatment, the client/patient must be diagnosed with a psychological disorder. Clinical diagnosis is the process of using assessment data to determine if the pattern of symptoms the person presents with is consistent with the diagnostic criteria for a specific psychological disorder set forth in an established classification system such as the DSM-5 or ICD-10 (both will be described shortly). Any diagnosis should have clinical utility, meaning it aids the mental health professional in determining the prognosis, the treatment plan, and possible outcomes of treatment (APA, 2013). Receiving a diagnosis does not necessarily mean the person requires treatment. This decision is made based upon how severe the symptoms are, the level of distress caused by the symptoms, symptom salience such as expressing suicidal ideation, risks and benefits of treatment, disability, and other factors (APA, 2013). Likewise, a patient may not meet the full criteria for a diagnosis but require treatment due to high levels of distress or impairement.

Symptoms that cluster together on a regular basis are called a syndrome. If they also follow the same, predictable course, we say that they are characteristic of a specific disorder. Classification systems for psychological disorders provide mental health professionals with an agreed upon list of disorders falling in distinct categories for which there are clear descriptions and criteria for making a diagnosis. Distinct is the key word here. People experiencing delusions, hallucinations, disorganized speech, disorganized behavior, and/or negative symptoms are different from people presenting with a primary clinical deficit in cognitive functioning that is not developmental in nature but has been acquired (i.e. they have shown a decline in cognitive functioning over time). The former would likely be diagnosed with a schizophrenia spectrum disorder while the latter would likely be diagnosed with a neurocognitive disorder (NCD). The latter can be further distinguished from neurodevelopmental disorders which manifest early in development and involve developmental deficits that cause impairments in social, academic, or occupational functioning (APA, 2013). These three disorder groups or categories can be clearly distinguished from one another. Classification systems also permit the gathering of statistics for the purpose of determining incidence and prevalence rates, they facilitate research on the etiology and treatment of disorders, and they conform to the requirements of insurance companies for the payment or reimbursement of service fees.

The most widely used classification system in the United States is the Diagnostic and Statistical Manual of Mental Disorders (DSM) currently in its 5th edition and produced by the American Psychiatric Association (APA, 2013). A text revision of this edition (DSM-5-TR) was published in 2022 with minor changes to some disorders, the addition of new disorders (e.g., Prolonged Grief Disorder), minor changes to language (e.g., intellectual disability was changed to intellectual developmental disorder), and further considerations of the impacts of culture, racism, and discrimination on diagnosis. Alternatively, the World Health Organization (WHO) publishes the International Statistical Classification of Diseases and Related Health Problems (ICD) currently in its 11th edition which came into effect in 2022. We will begin by discussing the DSM and then move to the ICD.

3.2.2. The DSM Classification System

3.2.2.1. A Brief History of the DSM

The DSM-5 was first published in 2013 with a text revision (DSM-5-TR) published in 2022. The DSM-5 took the place of the DSM IV-TR which was published in 2000. But the history of the DSM goes back to 1844 when the American Psychiatric Association published a predecessor of the DSM which was a “statistical classification of institutionalized mental patients” and “…was designed to improve communication about the types of patients cared for in these hospitals” (APA, 2013, p. 6). However, the first official edition of the DSM was published by the  American Psychiatric Association in 1952. The DSM evolved through four subsequent editions after World War II into a diagnostic classification system to be used by psychiatrists and physicians, as well as other mental health professionals. The Herculean task of revising the DSM IV-TR began in 1999 when the American Psychiatric Association embarked upon an evaluation of the strengths and weaknesses of the DSM in coordination with the World Health Organization (WHO) Division of Mental Health, the World Psychiatric Association, and the National Institute of Mental Health (NIMH). This resulted in the publication of a monograph in 2002 called, A Research Agenda for DSM-V. From 2003 to 2008, the APA, WHO, NIMH, the National Institute on Drug Abuse (NIDA), and the National Institute on Alcoholism and Alcohol Abuse (NIAAA) convened 13 international DSM-5 research planning conferences, “to review the world literature in specific diagnostic areas to prepare for revisions in developing both DSM-5 and the International Classification of Disease, 11th Revision (ICD-11)” (APA, 2013).

After the naming of a DSM-5 Task Force Chair and Vice-Chair in 2006, task force members were selected and approved by 2007, and workgroup members were approved in 2008. What resulted from this was an intensive process of “conducting literature reviews and secondary analyses, publishing research reports in scientific journals, developing draft diagnostic criteria, posting preliminary drafts on the DSM-5 website for public comment, presenting preliminary findings at professional meetings, performing field trials, and revisiting criteria and text”(APA, 2013).

What resulted was a “common language for communication between clinicians about the diagnosis of disorders” along with a realization that the criteria and disorders contained within were based on current research and may undergo modification with new evidence gathered (APA, 2013). Additionally, some disorders were not included within the main body of the document because they did not have the scientific evidence to support their widespread clinical use but were included in Section III under “Conditions for Further Study” to “highlight the evolution and direction of scientific advances in these areas to stimulate further research” (APA, 2013).

3.2.2.2. Elements of a Diagnosis

The DSM 5 states that the following make up the key elements of a diagnosis (APA, 2013):

• Diagnostic Criteria and Descriptors – Diagnostic criteria are the guidelines for making a diagnosis. When the full criteria are met, mental health professionals can add severity and course specifiers to indicate the patient’s current presentation. If the full criteria are not met, either no diagnosis is made or designators such as “other specified” or “unspecified” can be used. If applicable, an indication of severity (mild, moderate, severe, or extreme), descriptive features, and course (type of remission – partial or full – or recurrent) can be provided with the diagnosis. The final diagnosis is based on the clinical interview, text descriptions, criteria, and clinical judgment.
• Subtypes and Specifiers – Since the same disorder can be manifested in different ways in different individuals the DSM uses subtypes and specifiers to better characterize an individual’s disorder. Subtypes denote “mutually exclusive and jointly exhaustive phenomenological subgroupings within a diagnosis” (APA, 2013). For example, non-rapid eye movement sleep arousal disorders can have either a sleepwalking or sleep terror type. Enuresis is nocturnal only, diurnal only, or both. Specifiers are not mutually exclusive or jointly exhaustive and so more than one specifier can be given. For instance, binge eating disorder has remission and severity specifiers. Major depressive disorder has a wide range of specifiers that can be used to characterize the severity, course, or symptom clusters. Again the fundamental distinction between subtypes and specifiers is that there can be only one subtype but multiple specifiers.
• Principle Diagnosis – A principal diagnosis is used when more than one diagnosis is given for an individual (when an individual has comorbid disorders). The principal diagnosis is the reason for the admission in an inpatient setting or the reason for a visit resulting in ambulatory care medical services in outpatient settings. The principal diagnosis is generally the main focus of treatment.
• Provisional Diagnosis – If not enough information is available for a mental health professional to make a definitive diagnosis, but there is a strong presumption that the full criteria will be met with additional information or time, then a provisional specifier can be used. 

3.2.2.3. DSM-5 Disorder Categories

The DSM-5 includes the following categories of disorders:

Table 3.1. DSM-5 Classification System of Mental Disorders

3.2.3. The ICD-10

In 1893, the International Statistical Institute adopted the International List of Causes of Death which was the first edition of the ICD. The World Health Organization was entrusted with the development of the ICD in 1948 and published the 6th version (ICD-6), which was the first version to include psychological disorders. The ICD-11 was endorsed in 2019 by the 72nd World Health Assembly. The WHO states:

ICD is the foundation for the identification of health trends and statistics globally, and the international standard for reporting diseases and health conditions. It is the diagnostic classification standard for all clinical and research purposes. ICD defines the universe of diseases, disorders, injuries and other related health conditions, listed in a comprehensive, hierarchical fashion that allows for:

• easy storage, retrieval and analysis of health information for evidence-based decision-making;
• sharing and comparing health information between hospitals, regions, settings, and countries;
• and data comparisons in the same location across different time periods.

Source: http://www.who.int/classifications/icd/en/

The ICD lists many types of diseases and disorders and includes Chapter V: Mental and Behavioral Disorders. The list of mental disorders is broken down as follows:

• Organic, including symptomatic, mental disorders
• Mental and behavioral disorders due to psychoactive substance use
• Schizophrenia, schizotypal, and delusional disorders
• Mood (affective) disorders
• Neurotic, stress-related, and somatoform disorders
• Behavioral syndromes associated with physiological disturbances and physical factors
• Disorders of adult personality and behavior
• Intellectual developmental disorders
• Disorders of psychological development
• Behavioral and emotional disorders with onset usually occurring in childhood and adolescence
• Unspecified mental disorder

3.2.4. Harmonization of DSM-5 and ICD-11

As noted earlier, the ICD-11 took effect in 2022. According to the DSM-5, there is an effort to harmonize the two classification systems so that there can be a more accurate collection of national health statistics and design of clinical trials, increased ability to replicate scientific findings across national boundaries and to rectify the lack of agreement between the DSM-IV and ICD-10 diagnoses. (APA, 2013). Toward this goal of harmonization, the DSM-5-TR includes ICD codes for each of the psychological disorders.