Almost all mental disorders or conditions that may be a focus of clinical attention appear on Axis I, with a few exceptions that appear on Axis II. Axis I organizes mental disorders into 15 major groups of disorders, as presented in Table I. Most of the groups in Table I were created based on the similarity of symptoms of disorders within that group, although in some cases disorders are grouped together because of the typical age at which symptoms first appear (Disorders Usually First Diagnosed in Infancy, Childhood or Adolescence), or because of common etiology (Mental Disorders due to a General Medical Condition, Substance-Related Disorders, Adjustment Disorders). In many cases, an individual may receive more than one Axis I diagnosis, although some diagnoses by definition will preclude another diagnosis.
Each disorder on Axis I includes a set of diagnostic criteria, which are typically a combination of mono-thetic (i.e., all conditions of the criterion must be met) and polythetic (i.e., only some from among a larger set of conditions must be met) criteria. For example, to diagnosis Attention Deficit/Hyperactivity disorder, an individual must meet the following criteria: (a) either 6 or more symptoms (from among 9) of inattention, or 6 or more symptoms (from among 9) of hyperactivity-impulsivity (polythetic); (b) some symptoms are present and causing impairment before age 7 (monothetic); (c) impairment is seen in at least two settings, such as school and home (monothetic); (d) the symptoms clearly cause impairment in func-
Table I Examples of Disorders in Each of the 15 Major Groups Listed on Axis I of DSM-IV
Examples of Disorders
Disorders Usually First Diagnosed in Infancy,
Childhood, or Adolescence Delirium, Dementia, and Amnestic and Other
Cognitive Disorders Mental Disorders Due to a General Medical
Condition Substance-Related Disorders Schizophrenia and Other Psychotic Disorders Mood Disorders
Somatoform Disorders Factitious Disorders Dissociative Disorders
Sexual and Gender Identity Disorders
Impulse-Control Disorders Not Elsewhere Classified
Attention Deficit/Hyperactivity Disorder, Autistic Disorder
Dementia of the Alzheimer's Type, Vascular Dementia
Mood Disorder Due to a General Medical Condition (e.g., stroke, hypothyroidism)
Schizophrenia, Delusional Disorder, Schizoaffective Disorder
Posttraumatic Stress Disorder Somatization Disorder, Hypochondriasis Factitious Disorder
Dissociative Identity Disorder (formerly Multiple Personality Disorder),
Dissociative Amnesia Sexual Dysfunctions (e.g., Male Erectile Disorder), Paraphilias (e.g.,
Exhibitionism, Pedophilia), Gender Identity Disorder Anorexia Nervosa, Bulimia Nervosa Primary Insomnia, Narcolepsy, Sleep Terror Disorder Kleptomania, Pyromania, Pathological Gambling tioning (monothetic); and (e) the symptoms are not better accounted for by another mental or physical disorder (monothetic). Polythetic criterion sets have advantages and disadvantages. The primary advantage is that polythetic sets reduce the number of diagnostic categories required, since people with highly similar but nonidentical symptoms can receive the same diagnosis. If, by contrast, each and every criterion were required, such highly similar people would require different diagnoses. The primary disadvantage to polythetic criterion sets is symptom heterogeneity, where people with the same diagnosis may be quite different in terms of their symptoms. In fact, in the case of some disorders, it is possible that two individuals with the same diagnosis may not share a single symptom in common.
There are also disorders that appear on Axis I that do not have such clearly defined criterion sets. There are over 40 disorders that include "NOS" in their name, an abbreviation for Not Otherwise Specified. These disorders are diagnosed if the symptoms resemble those of another diagnosis but fail to meet the full criteria required for diagnosis. For example, Anxi ety Disorder NOS is a diagnosis for cases in which there is "prominent anxiety or phobic avoidance that do not meet the criteria for any specific Anxiety Disorder'' (p. 444) or meet criteria for Adjustment Disorder.
Also found for each disorder (other than NOS disorders) listed on Axis I are other sections providing more detailed information that may be of use to clinicians. The Diagnostic Features section provides an overview of the essential features of the disorder, along with examples and definitions of criteria and terms that are part of the criterion set for that disorder. The Subtypes and/or Specifiers section delineates subtypes of the disorder (e.g., Catatonic Subtype of Schizophrenia) or specifiers of the disorder (e.g., Post-partum Onset for Major Depressive Disorder), where applicable. The Recording Procedures section includes information to assist in reporting the correct name of the disorder and the associated five-digit code that corresponds to the disorder. These five-digit codes correspond to the codes listed in the International Classification of Disease (9th edition, with clinical modification), the diagnostic system of the
World Health Organization that includes both medical and mental disorders.
The Associated Features and Disorders section describes symptoms that, while not necessary for the diagnosis of the disorder, are often seen in persons with the disorder. This section also includes a listing of other mental disorders that are commonly comorbid (likely to co-occur) with the disorder, and includes a listing of laboratory findings, clinical findings from examination, and medical conditions that may be associated with the disorder. The Specific Age, Culture, or Gender Features section details information concerning how the symptoms of a disorder may differ as a function of these demographic variables, including how symptoms may present differently in children and the elderly, how particular symptoms of the disorder may present differently in different cultures, and the proportion of women and men among those with the disorder. The Prevalence section provides information estimating how common the disorder is thought to be. These estimates are taken from large-scale epidemiological studies when possible, and include estimates of point prevalence (prevalence at any point in time) as well as lifetime prevalence (the proportion of people that in their lifetimes will experience the disorder). The Course section details information concerning onset and progression of symptoms, as well as the prognosis for remission and for relapse. In this section are included the typical age (or ages) of onset, factors that may predispose one to develop the disorder, and information concerning whether symptoms may worsen or improve with age. Also included in this section are estimates of whether a disorder is likely to involve one episode, multiple episodes with symptom-free periods between episodes, or chronic unremitting symptoms. The Familial Pattern section summarizes evidence concerning whether the disorder and related disorders are more common in the first-degree biological relatives of those with the disorder than members of the general population. This section also summarizes the results of twin or adoption studies, when available. Finally, the Differential Diagnosis section provides information to assist the diagnostician in distinguishing the disorder from other disorders that may appear similar or that may share symptoms in common. This section highlights the differences between disorders that could possibly be confused (e.g., Major Depressive Disorder versus Adjustment Disorder with Depressed Mood or, in the elderly, Dementia).
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