The development of the ICD-11 Clinical Descriptions and Diagnostic Guidelines for Mental and Behavioural Disorders

Abstract

The World Health Organization is in the process of preparing the eleventh revision of the International Classification of Diseases (ICD-11), scheduled for presentation to the World Health Assembly for approval in 2017. The International Advisory Group for the Revision of the ICD-10 Mental and Behavioural Disorders made improvement in clinical utility an organizing priority for the revision. The uneven nature of the diagnostic information included in the ICD-10 Clinical Descriptions and Diagnostic Guidelines (CDDG), especially with respect to differential diagnosis, is a major shortcoming in terms of its usefulness to clinicians. Consequently, ICD-11 Working Groups were asked to collate diagnostic information about the disorders under their purview using a standardized template (referred to as a “Content Form”). Using the information provided in the Content Forms as source material, the ICD-11 CDDG are being developed with a uniform structure. The effectiveness of this format in producing more consistent clinical judgments in ICD-11 as compared to ICD-10 is currently being tested in a series of Internet-based field studies using standardized case material, and will also be tested in clinical settings.

The International Classification of Diseases and Related Health Problems (ICD), which is the international standard for health reporting and health information, is currently in its tenth revision (ICD-10). The World Health Organization (WHO) is in the process of preparing the eleventh revision (ICD-11), scheduled for presentation to the World Health Assembly for approval in 2017. By international treaty, WHO is assigned the responsibility “to establish and revise as necessary international nomenclatures of diseases, of causes of death and of public health practices” and “to standardize diagnostic procedures as necessary” (1). Within the context of WHO policies and procedures for the overall ICD revision, the WHO Department of Mental Health and Substance Abuse has technical responsibility for coordinating the development of the Chapter on Mental and Behavioural Disorders in ICD-11.

The purpose of this paper is to describe the guidance that the Department of Mental Health and Substance Abuse has provided to Working Groups engaged in the ICD-11 revision process, the priorities lying behind that guidance, the procedures implemented by the Department to help the revision process achieve its goals, and the nature of the diagnostic guidance that will be provided to health care professionals as a part of the Clinical Descriptions and Diagnostic Guidelines (CDDG) for ICD-11 Mental and Behavioural Disorders.

Disease classifications have been applied to a large and growing number of purposes, which can be grouped roughly into three major clusters: a) clinical uses; b) public health uses, including provision of a basis for health statistics and a shared language for health policy; and c) disease-related research. Addressing the central clinical purposes of a disease classification, and building on earlier work (2), the WHO has offered the following working definition of clinical utility: “the clinical utility of a classification construct or category for mental and behavioural disorders depends on: a) its value in communicating (e.g., among practitioners, patients, families, administrators); b) its implementation characteristics in clinical practice, including its goodness of fit (i.e., accuracy of description), its ease of use, and the time required to use it (i.e., feasibility); and c) its usefulness in selecting interventions and in making clinical management decisions” (3, p. 461).

On the basis of comments received, structured surveys of practitioners, and input from diverse professional organizations whose members treat individuals with mental and behavioural disorders, the International Advisory Group for the Revision of the ICD-10 Mental and Behavioural Disorders concluded that there was room for significant improvements in clinical utility and that these deserved to be a major guiding principle for the revision process (3,4). Moreover, in light of the rapidly changing state of scientific approaches to mental and behavioural disorders (5–7), the Advisory Group concluded that the revision must take into account well-validated and well-replicated results where they existed, but that it was premature to make still embryonic scientific understandings the major drivers of specific disease definitions. In short, clinical utility deserved to be an organizing priority for the revision so long as it did not sacrifice validity as established by the best available science.

To put the revision process in context, we begin this essay with a brief overview of ICD-10 Chapter on Mental and Behavioural Disorders, approved by the World Health Assembly in 1992. Notably, the time interval between the ICD-10 and ICD-11 revisions will have been the longest between ICD revisions since the process first began in the late 19th century. Unlike the other chapters in the ICD classification, which confined their content exclusively to the names of disorders plus inclusion and exclusion terms, a glossary of terms was developed in 1974 (8) to accompany the eighth revision of the ICD (ICD-8) (9), approved in 1966. As the introduction to the glossary states, “guidance to the… [mental disorders chapter] of ICD-8 has been added in the form of a glossary because it has become increasingly obvious that many key psychiatric terms are acquiring different meanings in different countries [and] unless some attempt is made to encourage uniformity of usage of descriptive and diagnostic terms, very little meaning can be attributed to the diagnostic side of statistics of mental illness based on the ICD and in many other ways communication between psychiatrists will become increasingly difficult” (8, p. 12).

The version of the ICD-10 that WHO member countries agree to use as the basis for reporting of health statistics is called the International Statistical Classification of Diseases and Related Health Problems (10) and is split into three volumes. Volume 1, known as the “tabular list”, contains a listing of all of the medical conditions included in ICD-10 in alphanumerical order, ranging from A00 to Z99. In this statistical version of the ICD-10, none of the diagnostic codes go beyond the fourth character (e.g., F31.0), with each character corresponding to a hierarchical level of the classification. For example, in the code F31.0, the “F” corresponds to Mental and Behavioural Disorders, “F3” corresponds to Mood (Affective) Disorders, the “F31” to Bipolar Affective Disorder, and “F31.0” to Bipolar Affective Disorder, Current Episode Hypomanic.

From the perspective of the WHO Department of Mental Health and Substance Abuse, different versions of the ICD-10 Classification of Mental and Behavioural Disorders were necessary to meet the needs of its various users. The ICD-10 statistical version of the classification contains short glossary-like definitions for each mental and behavioural disorder category, but “is not recommended for use by mental health professionals” and instead is intended for use by “coders or clerical workers and also serves as a reference point for compatibility with other classifications” (11, p. 1). For mental health professionals, the Department developed the CDDG for ICD-10 Mental and Behavioural Disorders (11), often referred to as the “blue book” because of its blue cover, which is “intended for general clinical, educational, and service use” (11, p. 1). For each disorder, a description of the main clinical and associated features is provided, followed by more operationalized diagnostic guidelines that are designed to assist mental health clinicians in making a confident diagnosis.

In addition, the CDDG add greater diagnostic specificity through more detailed categories not included in the statistical version of the classification, represented by 5th character codes. For example, 5th character codes are used to describe complications of acute substance intoxication (e.g., with trauma or other bodily injury, with delirium) and the course of schizophrenia (e.g., episodic with progressive deficit, incomplete remission). National modifications of the ICD-10 intended for use in clinical systems (e.g., the ICD-10-GM, the German Modification, or the ICD-10-CM, Clinical Modification for the United States) often also include these same 5th character codes, and in some cases assign alternative or additional 5th and even 6th character codes to provide additional specificity for local clinical use.

The WHO Department of Mental Health and Substance Abuse also developed Diagnostic Criteria for Research (DCR) (12) (the “green book”), with specified, operationalized diagnostic criteria for each ICD-10 category that were “deliberately restrictive” to allow for the “selection of groups of individuals whose symptoms and other characteristics resemble each other in clearly stated ways” (12, p. 1). Consequently, in contrast to the CDDG, which are designed to allow for cultural variability and clinical judgment, the DCR imposed fixed symptom thresholds (e.g., “at least four of the following”) and frequency/duration requirements (e.g., “at least twice a week for 3 months”).

The differences between the CDDG and the DCR reflect the different purposes of these two versions of the classification. In clinical settings, the function of the classification is to help the clinician to find the category that is most likely to provide relevant information for treatment and management. Arbitrary or non-consequential exclusion criteria are problematic because they increase false negatives, leaving the clinician with little guidance; as a result their use is minimized in the CDDG. The DCR, on the other hand, had the goal of identifying research populations that were more homogeneous in terms of underlying pathophysiology or treatment response (e.g., for clinical trials). Unfortunately, given limitations in the state of knowledge, such as the lack of biomarkers, narrow disorder definitions based on operationalized criteria (e.g., requirements for a specific frequency or duration of symptoms) have not, to date, improved homogeneity in these ways (13).

The third version of the ICD-10 Classification of Mental and Behavioural Disorders, intended for use in primary care (14), contains only 26 disorders, achieved in part by excluding rarely diagnosed disorders and in part by lumping disorders that are narrowly drawn in the other versions of the classification and that have similar management needs. It includes for each disorder presenting complaints, diagnostic features, differential diagnoses, and management guidelines.

DIAGNOSTIC GUIDELINES IN ICD-10

Each of the broad disorder groupings, or blocks, within the ICD-10 CDDG begins with an introductory section explaining the scope of what is contained within the block and general principles that apply to all of the disorders within it.

The diagnostic information included for each disorder is generally divided into three sections. The first section contains a description of the main clinical features as well as “any important but less specific associated features”. The second section consists of “Diagnostic Guidelines”, which are provided to “indicate the number and balance of symptoms usually required before a confident diagnosis can be made”. Although statements about the duration of symptoms are often included (e.g., the diagnostic guidelines for schizophrenia state that “symptoms… should have been clearly present for most of the time during a period of 1 month or more”) (11, p. 88), the introduction to the CDDG notes that such statements are “intended as general guidelines rather than strict requirements; clinicians should use their own judgment about the appropriateness of choosing diagnoses when the duration of particular symptoms is slightly longer or shorter than that specified” (11, p. 2). The third section, “Differential Diagnosis”, indicates other ICD-10 disorders that need to be distinguished from the disorder being described.

One factor potentially compromising the clinical utility of the ICD-10 CDDG is the variability of information in terms of both form and content across the various groupings and disorders. The Clinical Descriptions vary widely in length and in the scope of information included. Some focus almost entirely on the presenting features, whereas others contain extensive information about course, gender ratio, associated features and comorbidity. Moreover, the absence of headings makes it difficult for the clinician to locate information of particular interest. The Diagnostic Guidelines also vary greatly in terms of their format across the various sections. In some cases, the guidelines closely resemble diagnostic criteria sets, with lists of lettered items provided. Sometimes a minimum number of items is specified for a “definitive” diagnosis (e.g., at least two for Organic Personality Disorder). In many other cases, however, the diagnostic guidelines are presented as a paragraph of text (e.g., for Post-Traumatic Stress Disorder, PTSD), and sometimes are missing altogether (e.g., for Trance and Possession Disorders).

The greatest degree of variability is in the Differential Diagnosis sections. For a small minority of blocks (e.g., F40-F48 Neurotic, Stress-Related, and Somatoform Disorders), there are sections on differential diagnosis for a majority of the disorders. In most other blocks, however, Differential Diagnosis sections have been included for only a small minority of disorders, often on an apparently idiosyncratic basis. For example, the only disorder in F20-F29 (Schizophrenia, Schizotypal, and Delusional Disorders) with a differential diagnosis section is F20.0 Paranoid Schizophrenia, and the only disorder in F30-F39 (Mood Disorders) with a differential diagnosis section is F34.0 Cyclothymia. Moreover, for those disorders that have a Differential Diagnosis section, there is considerable variability in terms of format and content. For many disorders, the section simply includes a list of disorders preceded by the word “Consider” (e.g., all of the disorders in F00-F09 Organic Mental Disorders), whereas for others there are paragraph-long discussions (e.g., the differential diagnosis for Specific Phobias).

DEVELOPMENT OF THE ICD-11 DIAGNOSTIC GUIDELINES

The uneven nature of the diagnostic information included in the ICD-10 CDDG, especially with regard to the clinically important task of determining a differential diagnosis, has been identified as a major shortcoming in terms of its usefulness to clinicians. This variability in terms of format and content likely reflects the lack of standardized guidance for the preparation of the various sections, each of which was developed by different sets of experts.

Consequently, an initial goal of the ICD-11 CDDG development process was to create a mechanism to ensure consistent and relatively uniform provision of diagnostic information across the various categories. To facilitate this, ICD-11 Working Groups were asked to collate diagnostic information about the disorders under their purview using a standardized template (referred to as a “Content Form”) that contained prescribed sections (see Table1). Because the WHO has final editorial responsibility for the ICD-11 material, the Department of Mental Health and Substance Abuse wanted to ensure that Working Groups understood that they were developing source material that would be used as a basis for the development of the CDDG as well as other versions of the ICD-11. The Content Form was thus framed in light of these objectives, and was designed to provide a combination of technical, administrative, and clinical information.

Table 1.

Content Form used by ICD-11 Working Groups

I.  Category Name

II.  Relationship to ICD-10

A.  Equivalent ICD-10 Alphanumeric Code and Category Name

B.  Relationship of Proposed Category to ICD-10 (select one by circling number)

1.  Same category name as ICD-10; no or minor changes in concept

2.  Same category name as ICD-10; substantive changes in concept

3.  New category name; no or minor changes in concept

4.  New category name; substantive changes in concept

5.  New category (does not exist in ICD-10)

III.  Primary “Parent” Category

IV.  Secondary “Parent” Categories

V.  “Children” or Constituent Categories

VI.  Synonyms

VII.  Definition

VIII.  Diagnostic Guidelines

IX.  Functional Properties (if applicable)

X.  Temporal Qualifiers (if applicable)

XI.  Severity Qualifiers (if applicable)

XII.  Differential Diagnosis

XIII.  Differentiation from Normality

XIV.  Developmental Presentations

XV.  Course Features

XVI.  Associated Features and Comorbidities (as known and relevant)

A.  Associated symptoms and psychiatric disorders

B.  Associated physical symptoms and medical conditions

C.  Associated laboratory findings

D.  Associated functional limitations and restrictions

XVII.  Culture-Related Features

XVIII.  Gender-Related Features

XIX.  Assessment Issues

Additional References (not already included in above sections)

Specifically, a number of sections of the Content Form were included in order to meet certain requirements of the overall ICD-11 classification model (i.e., relationship to ICD-10, primary parent category, secondary parent category, “children” or constituent categories, synonyms, functional properties, temporal qualifiers, and severity qualifiers). The sections “primary and secondary parent category” and “children or constituent categories” indicate the position of the category in the ICD-11 hierarchy. For example, the parent category for the diagnostic grouping Body Focused Repetitive Behaviour Disorders is Obsessive-Compulsive and Related Disorders, and its “children” and constituent categories include Excoriation Disorder, Trichotillomania, and Other Body-Focused Repetitive Behaviour Disorder.

The sections “functional properties”, “temporal qualifiers” and “severity qualifiers” were also included for technical reasons. Ideally, mental disorders should be defined in terms of symptoms and not include activity limitations or participation restrictions, which should be classified using WHO's International Classification of Functioning, Disability and Health (15). However, given that for mental disorders it is sometimes necessary to use functional status to set the threshold with normality (e.g., the diagnostic threshold for phobias depends on the extent to which they impact the patient's functioning) (4), the “functional properties” section is used to indicate the rationale for using functional limitations in the diagnostic definition. The sections for temporal and severity qualifiers are used only in situations where a temporal term (e.g., “chronic”) or a severity term (e.g., “severe”) is used as part of the disorder name. In such situations, these sections serve to provide a definition for the term. The remaining sections of the Content Form contain diagnostic information that is used as the basis for the ICD-11 CDDG for the disorder, with relevant references.

ELEMENTS OF THE ICD-11 CLINICAL DESCRIPTIONS AND DIAGNOSTIC GUIDELINES

Using the information provided in the Content Form as source material, ICD-11 CDDG are being developed by the WHO in consultation with the Working Groups according to a uniform structure. The structure is intended to enhance the clinical utility of ICD-11 CDDG by making it easier for users to locate information of interest and by ensuring that the amount and type of information provided for each disorder would be consistent across the manual. A summary of the categories of information to be provided for each category in the CDDG appears in Table2. Each of these sections is discussed in detail below, accompanied by the corresponding section from the proposed ICD-11 CDDG for PTSD (16) as an illustrative example.

Table 2.

Standard format for ICD-11 Clinical Descriptions and Diagnostic Guidelines

Category Name

Brief Definition (100 - 125 words)

Inclusion Terms

Exclusion Terms

Essential (Required) Features

Boundary with Normality (Threshold)

Boundary with Other Disorders (Differential Diagnosis)

Coded Qualifiers/Subtypes

Course Features

Associated Clinical Presentations

Culture-Related Features

Developmental Presentations

Gender-Related Features

Definition

The definition of the disorder serves as a summary statement of the common essential features and is roughly 100 to 125 words in length. It will appear in the statistical versions of ICD-11. For example, the definition proposed for PTSD (Table3, upper portion) is a summarized version of the PTSD essential features (Table 3, lower portion).

Table 3.

Proposed ICD-11 Clinical Descriptions and Diagnostic Guidelines for Post-Traumatic Stress Disorder (PTSD): definition and essential features

Definition

Post-Traumatic Stress Disorder (PTSD) is a disorder that develops following exposure to an extremely threatening or horrific event or series of events characterized by: 1) re-experiencing the traumatic event(s) in the present in the form of vivid intrusive memories, flashbacks, or nightmares, typically accompanied by strong and overwhelming emotions such as fear or horror, and strong physical sensations; 2) avoidance of thoughts and memories of the event(s), or avoidance of activities or situations reminiscent of the event(s); and 3) persistent perceptions of heightened current threat, for example as indicated by hypervigilance or an enhanced startle reaction to stimuli such as unexpected noises. The symptoms must last for at least several weeks and cause significant impairment in personal, family, social, educational, occupational or other important areas of functioning.

Essential features Exposure to an event or situation (either short- or long-lasting) of an extremely threatening or horrific nature. Such events include, but are not limited to, natural or human-made disasters; combat; serious accidents; torture; sexual violence; terrorism; assault; acute life-threatening illness (such as a heart attack); witnessing the threatened or actual injury or death of others in a sudden, unexpected, or violent manner; and experiencing the sudden, unexpected or violent death of a loved one. Following the traumatic event or situation, the development of a characteristic syndrome lasting for at least several weeks, consisting of three core elements: Re-experiencing the traumatic event in the present, in which the event(s) is not just remembered but is experienced as occurring again in the here and now. This typically occurs in the form of vivid intrusive images or memories; flashbacks, which can vary from mild (there is a transient sense of the event occurring again in the present) to severe (there is a complete loss of awareness of present surroundings); or repetitive dreams or nightmares that are thematically related to the traumatic event(s). Re-experiencing is typically accompanied by strong or overwhelming emotions, such as fear or horror, and strong physical sensations. Re-experiencing in the present can also involve feelings of being overwhelmed or immersed in the same intense emotions that were experienced during the traumatic event, and may occur in response to reminders of the event. Reflecting on or ruminating about the event(s) and remembering the feelings that one experienced at that time do not constitute re-experiencing. Deliberate avoidance of reminders likely to produce re-experiencing of the traumatic event(s). This may take the form either of active internal avoidance of relevant thoughts and memories, or external avoidance of people, conversations, activities, or situations reminiscent of the event(s). In extreme cases the person may change his or her environment (e.g., move to a different city or change jobs) to avoid reminders. Persistent perceptions of heightened current threat, for example as indicated by hypervigilance or an enhanced startle reaction to stimuli such as unexpected noises. Hypervigilant persons constantly guard themselves against danger and feel themselves or others close to them to be under immediate threat either in specific situations or more generally. They may adopt new behaviours designed to ensure safety (e.g., only sit in certain places on trains, repeatedly check in vehicles' rear-view mirror). The disturbance causes significant impairment in personal, family, social, educational, occupational or other important areas of functioning. If functioning is maintained only through significant additional effort, or is significantly impaired in comparison with the individual's prior functioning or what would be expected, then he or she would be considered impaired due to the disturbance.

Essential (required) features

This section serves to provide relatively explicit guidance regarding the essential features needed to confidently make the diagnosis. The essential features represent those symptoms or characteristics that a clinician could reasonably expect to find in all cases of the disorder. While these lists of essential features superficially resemble diagnostic criteria in their overall format, for the most part they lack the specific and arbitrary duration thresholds and “pick lists” of items that characterize the diagnostic criteria sets in DSM-5 and the ICD-10 DCR. Instead, these diagnostic guidelines are intended to conform to the way clinicians actually make psychiatric diagnosis, i.e., with the flexible exercise of clinical judgment.

Artificially precise language has generally been avoided through the use of phrases such as “including”, “characterized by”, or “usually”, to indicate that some number of symptoms from the list should be present but that the precise number is best left to the clinician's judgment. Such flexibility in language allows the clinician to differentially weigh those symptoms that are particularly severe and impairing, which is generally not possible in operationalized criteria sets because of the complexity this would require. Moreover, an effort has been made to order the essential features according to their importance to the diagnosis.

Although for most disorders setting requirements for a minimum number of symptoms is generally avoided, in some cases symptom thresholds are provided if they have been empirically established or there is another compelling reason for such a threshold. For example, the diagnosis of schizophrenia as proposed for ICD-11 requires the presence of at least two of seven symptoms for a period of at least one month. In contrast, the proposed essential features section for PTSD (Table3, lower portion) does not include a specific duration requirement, nor does it include complex lists of symptoms with precise cut-offs.

Boundary with normality

This section provides the clinician with diagnostic guidance regarding the differentiation of normal variation in characteristics that may underlie or be similar to the disorder and conditions that are considered to be psychopathological (see Table4, upper portion).

Table 4.

Proposed ICD-11 Clinical Descriptions and Diagnostic Guidelines for Post-Traumatic Stress Disorder (PTSD): boundaries with normality and other conditions

Boundary with normality A history of exposure to an event or situation of an extremely threatening or horrific nature does not in itself indicate the presence of PTSD. Many people experience such stressors without developing a disorder. Rather, the presentation must meet the above diagnostic requirements of the disorder. Normal acute reactions to traumatic events can show all the symptoms of PTSD including re-experiencing, but these begin to subside fairly quickly (e.g., within one week) after the event terminates or removal from the threatening situation. If clinical intervention is warranted in these situations, assignment of the category Acute Stress Reaction from the chapter on Factors Influencing Health Status and Encounters with Health Services (i.e., a non-disorder category) is generally most appropriate. PTSD symptoms may also be observed in situations where the stress is continuing and removal is not possible (e.g., war). Under these conditions, PTSD can be differentiated from normal chronic stress reactions by slow, limited, or lack of adaptation to the stressful situation and the presence of a substantially greater degree of continuing distress and interference with functioning.

Boundary with other conditions In Complex PTSD, people have symptoms that meet the definitional requirements of PTSD plus the added elements of sustained and pervasive difficulties in emotion regulation, negative beliefs about self, and interpersonal functioning. Unlike Adjustment Disorder, which can persist for up to six months after stressors of any severity, PTSD can only be diagnosed if the individual has been exposed to a severe, usually life-threatening, stressor and presents with the three core PTSD symptoms. In some cases, situational or conditioned specific phobias can arise after being exposed to a traumatic event but PTSD and phobias can be differentiated particularly by the absence of re-experiencing. Although in phobic responses there may be powerful memories of the event in response to which the individual experiences anxiety, the memories are experienced as belonging to the past. In PTSD, panic attacks can be triggered by reminders of the traumatic event(s) or in the context of re-experiencing. The presence of panic attacks that occur entirely in the context of event reminders or re-experiencing does not warrant an additional, separate diagnosis. In a Depressive Episode, intrusive memories are not experienced as occurring again in the present, but as belonging to the past, and they are often accompanied by rumination. However, Depressive Episodes commonly co-occur with PTSD; if the definitional requirements are met for both, both conditions should be diagnosed. In PTSD, as opposed to Schizophrenia Spectrum and Other Primary Psychotic Disorders, the hallucinatory experiences and delusional beliefs are limited to flashbacks or episodes of re-experiencing related to an identifiable traumatic event.

Strategies for setting this threshold include specifying those aspects of the disorder that are indicative of its pathological nature and indicating typical false positives (i.e., clinical presentations that would be considered non-pathological). For many disorders (e.g., Generalized Anxiety Disorder), the presence of functional impairment or distress is required to make this distinction. In these cases, the rationale for this has been explicitly provided in the “functional properties” section of the Content Form, as described above (see Table1).

Boundary with other conditions (differential diagnosis)

This section indicates those disorders that should be considered in the differential diagnosis, particularly other disorders that share presenting symptoms or features. For each of these disorders, the features that serve to differentiate it from the index disorder are described. That is, this section is not simply a list of disorders that should be distinguished from the disorder being described, but rather provides guidance to the clinician about how to make this differentiation. Moreover, as illustrated in the PTSD example in the lower portion of Table4, if a disorder can be diagnosed concurrently, the circumstances in which this is permitted are elucidated.

Course features

This section of the guidelines provides clinically relevant information regarding the typical course of the disorder, which is defined broadly to include information about age of onset, whether the disorder is persistent or episodic, duration, its likely progression (or remission) over time, and its temporal relationship to life stressors and other disorders (see Table5, upper portion).

Table 5.

Proposed ICD-11 Clinical Descriptions and Diagnostic Guidelines for Post-Traumatic Stress Disorder (PTSD): course and associated features

Course features Onset of PTSD may be gradual or acute. Typically, onset arises soon after the traumatic event (generally within one month to 6 months). However, onset may occur after immediate threats to survival and other life stressors have subsided. In a small number of cases, the diagnostic threshold may not be met for many years after the traumatic event, with clinically significant PTSD symptoms emerging following other life stressors not necessarily associated with the original traumatic event(s). The course is often fluctuating and recovery is more common than not. Epidemiological studies suggest that in one third or more of untreated cases, PTSD persists for years, although a briefer pattern may be found where PTSD has arisen in the context of war or large-scale traumatic events. Individuals with long-lasting PTSD symptoms may eventually develop Complex PTSD. Predisposing factors, including personality traits (e.g., negative affectivity), exposure to previous trauma, or previous history of psychiatric illness, may lower the threshold for the development of PTSD after exposure to a traumatic stressor or aggravate its course. Associated features Common symptom presentations of PTSD may also include general dysphoria, dissociative symptoms, somatic complaints, suicidal ideation and behaviour, social withdrawal, excessive alcohol or drug use to avoid re-experiencing or to manage emotional reactions, and anxiety symptoms (including panic and obsessions/compulsions) in response to trauma memories or reminders of the trauma. The emotional experience of people with PTSD commonly includes anger, shame, sadness, humiliation, or guilt, including survivor guilt. Common co-occurring conditions include anxiety disorders, depressive disorders, and Substance Dependence or Harmful Use of Substances. The latter may reflect attempts to avoid reminders of the traumatic event(s). Further, prevalence rates of PTSD have been found to be high in individuals diagnosed with Schizophrenia and Bipolar Disorder. Somatic complaints such as headache, breathing difficulties and altered somatic perceptions, are common as an aspect of PTSD. PTSD is also associated with increased risk of numerous medical conditions including, but not limited to, circulatory, cardiovascular, gastrointestinal, musculoskeletal, and dermatological disorders, as well as with increased mortality.

Associated features

Associated features are not part of the essential characteristics of the disorder, because they are not diagnostically determinative, but are so frequently associated with the disorder that they help the clinician recognize the variations in its presentation (see Table5, lower portion). This section is also used for alerting the clinician to the likelihood that certain clinically important associated symptoms and/or disorders may be present which may require their own assessment and treatment.

Culture-related features

This section provides brief information regarding cultural considerations in making the diagnosis (see Table6, upper portion). Despite the international nature of the ICD, there was relatively little information about culture-related features in the ICD-10 CDDG.

Table 6.

Proposed ICD-11 Clinical Descriptions and Diagnostic Guidelines for Post-Traumatic Stress Disorder (PTSD): culture-related features and developmental presentations

Culture-related features

Culturally sanctioned and recognized expressions or idioms of distress, explanatory beliefs, and cultural syndromes may be a prominent part of the trauma response. They may influence PTSD symptomatology and comorbidity particularly through somatization as well as other emotional, cognitive and behavioural expressions of distress. For example, cultural idioms of distress following exposure to trauma may manifest through somatic symptoms, like ohkumlang (tiredness) and bodily pain among tortured Bhutanese refugees; symptoms like possession states in Guinea Bissau, Mozambique, Uganda, and Bhutanese refugees; susto (fright) among Latino populations; kit chraen (thinking too much) and sramay (flashbacks of past traumas in the form of dreams and imagery that spill over into waking life) in Cambodia. These cultural idioms are not equivalent to PTSD, but influence its presentation and interpretation.

Developmental presentations

PTSD can occur at all ages, but the response can differ depending on the age and developmental stage of the individual. In younger children, responses may include disorganization, agitation, temper tantrums, clinging, excessive crying, social withdrawal, separation anxiety, distrust; trauma-specific reenactments, such as in repetitive play or drawings; night terrors or frightening dreams without clear content; sense of foreshortened future; and impulsivity. Self-injurious or risky behaviours are more frequent in adolescence. Prevalence estimates of PTSD are relatively low in older persons, and low compared to other anxiety disorders in older populations. In general there is a decline in PTSD symptom severity over the life course, although findings on the overall course of PTSD across the lifespan remain inconclusive.

Developmental presentations

This section describes how symptom presentations may differ according to the developmental stage of the individual, including childhood, adolescence, and older adulthood (see Table6, lower portion). Many disorders traditionally thought of as “adult disorders” (e.g., depression) can present during childhood. In such instances, the symptom descriptions may be developmentally inappropriate (e.g., children with PTSD may repetitively re-enact the trauma in play rather than report “flashbacks”) or the disorder may manifest in different ways (e.g., children with depression may present with irritable mood, rather than depressed mood).

Similarly, many if not most disorders that are traditionally thought of as “childhood disorders” can persist into adulthood, with concomitant alterations in their presentation (e.g., Attention-Deficit/Hyperactivity Disorder, Autism Spectrum Disorder). Moreover, the developmental differences across the various stages of childhood (e.g., toddlerhood vs. primary school age vs. adolescence) may also result in varying presentations across the lifespan. Also included in this section are developmental variations that might occur in geriatric patients, among whom mental disorders, especially mood disorders (17), are more likely to be under-diagnosed.

Gender-related features

This section covers gender-related diagnostic issues. These range from gender-linked differences in symptom presentation to gender ratios in terms of prevalence both in the community and in clinical settings.

FIELD STUDIES OF PROPOSED ICD-11 DIAGNOSTIC GUIDELINES

The ICD-11 CDDG were developed with the goal of improving clinical utility while maintaining diagnostic reliability. However, whether this is in fact the case remains an empirical question. The WHO is conducting both Internet-based and clinic-based field trials for the mental disorders section of ICD-11, which are designed to investigate both the clinical utility and the diagnostic reliability of the proposed CDDG.

The Internet-based field studies are designed to assess the utility of proposed changes in the diagnostic system, using standardized case material within an experimental design to test whether the ICD-11 CDDG produce more consistent diagnostic behaviour than do the ICD-10 CDDG among a global, multilingual, and multidisciplinary sample of approximately 12,000 mental health professionals from more than 130 countries (see www.globalclinicalpractice.net to register in any of nine languages). Generally, this involves having participants apply either the ICD-10 or ICD-11 CDDG (based on random assignment) to case scenarios validated by multiple experts, so that the participant's adherence to the expert diagnosis can be assessed.

A total of approximately 12 major Internet-based field studies are being conducted in different diagnostic areas. Results available to date indicate superior adherence to ICD-11 CDDG as compared to ICD-10 CDDG, with more consistent diagnostic conclusions across clinicians, countries, and languages, suggesting that the ICD-11 versions are easier to apply and produce more accurate results.

While the Internet-based field studies represent the best and most efficient method for testing the proposed CDDG using a large sample of clinicians from around the world, it is also important for the guidelines to be tested in real clinical settings. Clinic-based field studies of the clinical utility and reliability of proposed CDDG will also be conducted via the WHO's network of International Field Study Centres. Clinic-based field studies will involve pairs of clinicians applying the ICD-11 CDDG to real patients, and will provide substantive data regarding inter-rater reliability and clinicians' assessment of the usefulness of the guidelines. Clinic-based field studies will also provide an opportunity to test other questions that can only be investigated in patient care settings (e.g., whether the ICD-11 guidelines lead to a reduction in the proportion of cases that result in “unspecified” diagnoses).

CONCLUSIONS

The structure presented above for each category in the ICD-11 CDDG is expected to enhance the clinical utility of the manual by providing clearly organized, consistent information across disorders that is flexible enough to allow for cultural variation and the exercise of clinical judgment. The utility and effectiveness of this format in producing more consistent clinical judgments in ICD-11 as compared to ICD-10 is currently being tested in a series of Internet-based field studies using standardized case material, and will also be tested in clinical settings.

Although previous versions of the ICD, as well as the DSM, have typically emphasized clinical utility as their highest priority, this area has in fact received almost no systematic attention (2,18,19). Based on its mission as a global public health agency, the WHO is particularly interested in the clinical utility of the classification because it is critical to the interface between clinical practice and health information. A mental disorders classification that is difficult and cumbersome to implement and does not provide information of value to the clinician has no hope of being implemented accurately at the encounter level in real-world health care settings (3,20,21). As a result, important opportunities to improve clinical practice will be lost. Moreover, a diagnostic system characterized by poor clinical utility cannot be an effective tool for generating data based on those encounters that provide a valid basis for health programs and policies, or for global health statistics.