Because they believe they are medically ill, individuals with illness anxiety disorder are encountered far more frequently in medical than in mental health settings. The majority of individuals with illness anxiety disorder have extensive yet unsatisfactory medical care, though some may be too anxious to seek medical attention. They generally have elevated rates of medical utilization but do not utilize mental health services more than the general population. They often consult multiple physicians for the same problem and obtain re- peatedly negative diagnostic test results. At times, medical attention leads to a paradoxical exacerbation of anxiety or to iatrogenic complications from diagnostic tests and proce- dures. Individuals with the disorder are generally dissatisfied with their medical care and find it unhelpful, often feeling they are not being taken seriously by physicians. At times, these concerns may be justified, since physicians sometimes are dismissive or respond with frustration or hostility. This response can occasionally result in a failure to diagnose a medical condition that is present.
Prevalence estimates of illness anxiety disorder are based on estimates of the DSM-III and
DSM-IV diagnosis hypochondriasis. The 1- to 2-year prevalence of health anxiety and/ or disease conviction in community surveys and population—based samples ranges from 1.3% to 10%. In ambulatory medical populations, the 6-month/1-year prevalence rates are be- tween 3% and 8%. The prevalence of the disorder is similar in males and females.
The development and course of illness anxiety disorder are unclear. Illness anxiety disor- der is generally thought to be a chronic and relapsing condition with an age at onset in early and middle adulthood. In population-based samples, health-related anxiety in- creases with age, but the ages of individuals with high health anxiety in medical settings do not appear to differ from those of other patients in those settings. In older individuals, health—related anxiety often focuses on memory loss; the disorder is thought to be rare in children.
Environmental. Illness anxiety disorder may sometimes be precipitated by a major life stress or a serious but ultimately benign threat to the individual's health. A history of child- hood abuse or of a serious childhood illness may predispose to development of the disor- der in adulthood.
Course modifiers. Approximately one-third to one-half of individuals with illness anx- iety disorder have a transient form, which is associated with less psychiatric comorbidity, more medical comorbidity, and less severe illness anxiety disorder.
The diagnosis should be made with caution in individuals whose ideas about disease are congruent with widely held, culturally sanctioned beliefs. Little is known about the phe- nomenology of the disorder across cultures, although the prevalence appears to be similar across different countries with diverse cultures.
Functional Consequences of Illness Anxiety Disorder function and health-related quality of life. Health concerns often interfere with interper- sonal relationships, disrupt family life, and damage occupational performance.
Other medical conditions. The first differential diagnostic consideration is an underly- ing medical condition, including neurological or endocrine conditions, occult malignan- cies, and other diseases that affect multiple body systems. The presence of a medical condition does not rule out the possibility of coexisting illness anxiety disorder. If a med- ical condition is present, the health-related anxiety and disease concerns are clearly dis- proportionate to its seriousness. Transient preoccupations related to a medical condition do not constitute illness anxiety disorder.
Adjustment disorders. Health-related anxiety is a normal response to serious illness and is not a mental disorder. Such nonpathological health anxiety is clearly related to the medical condition and is typically time-limited. If the health anxiety is severe enough, an adjustment disorder may be diagnosed. However, only when the health anxiety is of suf- ficient duration, severity, and distress can illness anxiety disorder be diagnosed. Thus, the diagnosis requires the continuous persistence of disproportionate health—related anxiety for at least 6 months.