This category refers to motor or sensory symptoms superficially suggestive of nervous system disease although not generated by organic pathology. Rather the symptoms are judged as being due to psychological factors by virtue of the timing of their onset or exacerbation in relation to psychological stressors. The diagnosis excludes symptoms that are deliberately feigned and symptoms limited to pain or sexual dysfunction. Some authors argue, however, that doctors’ ability to discern deception and thereby to distinguish conscious from unconscious mechanisms is too limited to form the basis of the nosology. The term conversion derives from an early Freudian notion that in this disorder affect, considered as a quantum of energy, is transformed into somatic excitation. No one thoughtfully holds this view or indeed the theory of mental energy where it was embedded, but the term conversion is mummified in the DSM, obscuring our lack of a theoretic consensus about the actual genesis of such symptoms. Alternatively, the International Classification of Diseases (ICD) considers such symptoms under the rubric of dissociation that posits an etiologic theory, although not a well-established one.

Nonorganic symptoms are common in clinical practice: At least one third of symptoms presented to primary care physicians are medically unexplained.¹ Epidemiologic data for conversion disorder—difficult to obtain because of the requirement that the symptom be medically unexplained, information that may not be accessible by the interview of the sufferer—suggest a relatively low population prevalence, in the vicinity of 1 to 2 per 1,000 in a 12-month prevalence.² The frequency in women may exceed that in men. However, among those seeking medical care, and especially in specialty settings, the figures are markedly different. For example, in a consecutive series of 300 outpatients seen in a neurology clinic in Scotland, symptoms were considered “not at all explained” by organic pathology in 11% and only “somewhat explained” by disease in 19%.³ The point prevalence of conversion disorder among Danish medical inpatients was 1.5%⁴ and 2.9% among neurology clinic attenders.⁵

The outcome of conversion symptoms is not fully known. Studies from tertiary centers may overstate chronicity—a degree of chronicity having been a factor in the patients coming to such a venue—and population-based outcome studies are not available. However, commonly the disorder evolves unfavorably.
Often conversion symptoms do not resolve or, if they do, other somatoform symptoms may develop. If the field of view of outcome is widened, patients are seen to do poorly in regard to other benchmarks, such as mood symptoms, employment, and family functioning.⁶ In general, patients with somatoform disorders are as disabled as patients with other major mental disorders.⁷

Some patients present not an isolated nonorganic symptom but a seeming lifestyle devoted to somatic complaints without explanatory organic disease. These more pervasive disorders are classified as somatization disorder (SD) if they meet arbitrary criteria of severity, or as undifferentiated somatoform disorder (USD). In research settings other categorizations have been proposed; the data appear to show that patients just short of meeting criteria for SD generally resemble their more severely and pervasively affected counterparts. Unsurprisingly, a continuum of severity exists with SD at the most severe end.

The formal criteria for SD require the early onset (before age 30 by criterion, but far earlier in most instances) of multiple somatic complaints with consequent medical help-seeking or functional impairment. Specifically, the patient must report four pain symptoms, two gastrointestinal symptoms, one sexual symptom, and one conversion symptom. In each instance, no explanatory disease can be found after appropriate evaluation.

The criteria for SD include only somatic symptoms, albeit somatic symptoms without a basis in somatic disease. However, mental symptoms feature prominently in the presentation of patients with somatoform disorders. Briquet—the 19th century French physician who made an inventory of the symptoms of hysteria—knew this well and emphasized the “affective predominance” and lability of the hysteric. Psychogenic amnesia, which cannot be classified as “somatoform” because it is mental, resembles a conversion symptom in all other respects. Rates of mood disorder and other psychiatric syndromes are high in populations with somatoform symptoms (see subsequent text). Less appreciated in textbooks, although well known to clinicians, is the thought disorder, or incapacity to organize coherent narratives (especially of illness), that is highly prevalent in patients with nonorganic somatic symptoms. Such patients provide vague, circumstantial, indirect, and egocentric reports that lead to frustration and puzzlement on the part of the interviewer.⁸

As with conversion disorder, the prevalence in medical settings of more pervasive somatization substantially exceeds the population prevalence. In a Dutch general practice survey, 0.5% met the criteria for SD but an additional 17.7% met the broader criteria for USD.⁹ In the Scandinavian inpatient study mentioned earlier, the rate of DSM-IV SD was 1.5% and that of USD 10.1%.⁴ In a neurology clinic sample, the rates of SD and USD were 1.1% and 17.5% respectively.⁵ More than a third met the criteria for
one or the other type of the somatoform disorders. The effect of a prevalence of nonorganic disease in medical practice in this range—one patient in six or even one patient in three—is enormous.

Patients with somatoform disorders may present with a specific “diagnosis,” either provided by a clinician or self-attributed. These putative diseases vary in their evidentiary basis and validity (see Table 14.1). Patients’ involvement in Internet groups focused on these diagnoses can complicate assessment and treatment. Further, prognosis may vary inversely with the patient’s commitment to a diagnostic label or to a somatic explanation for the symptoms.¹⁰

Other psychiatric diagnoses are common in patients with somatoform disorders. In the study of patients in a neurology clinic already cited, 60.5% of those with somatoform disorders met criteria for another psychiatric disorder.⁵ Anxiety or depressive disorder cooccur in approximately one fourth of the patients,⁹ but other conditions, for example eating disorders, should be considered and sought in the psychiatric evaluation.

This category comprises patients who report pain, with its associated distress and impairment in function, when psychological factors are judged to be significant in the origin, maintenance, or severity of the pain, and when neither feigning or intentional production of the pain nor an explanatory mood or anxiety disorder is present. A concurrent organic disorder may be present; if so, the psychological factors are nonetheless judged to play a major role in the pain disorder.

How is one to judge that the psychological factors are significant? In practice, the nonpsychiatric physician often makes the judgment; the clinician considers that the reports of pain are incompatible with an organic lesion if one is present, or excessive compared with patients with similar disorders whom the physician has treated. Since the psychiatrist’s
experience is likely to be more limited than, say, the orthopaedic surgeon’s experience of low back pain after surgery, the somewhat odd situation obtains where the nonpsychiatrist offers or clinches the psychiatric diagnosis. Faced with such a patient, the neuropsychiatrist may not find compelling psychological factors by interview. However, as most people have some psychological stressor at any given time, and because the tendency of patients not to acknowledge psychological conflicts must be taken into account, psychiatrists characteristically have a low threshold for attributing causal power to presumed psychological factors. Further consideration of the problem of pain evaluation and management is provided in a separate chapter in this volume.

In these behavioral syndromes, symptoms (whether somatic or mental) are deliberately produced. The production may consist in feigning of symptoms or in creating them by self-injurious behavior, for example, production of fever by self-injection with contaminated material. Factitious disorder is distinguished from malingering by the goal or motivation of the behavior. In the former, the goal is the patient’s assumption of the sick role; in the latter some practical incentive, such as financial gain or legal exculpation, is sought.

Malingering may be distinctly recognizable and even represent rational problem-solving behavior in certain social settings, such as prisons. Some have argued that external incentives, notably financial ones, drive much pseudosickness behavior, from whiplash through post-traumatic stress disorder. However, the motivations for behavior are rarely easy to discern unambiguously. Although it may seem to some that seeking financial gain is so naturally a preponderant motive that its pursuit demands no further explanation, others believe that the behavior of many patients considered to be malingerers is complexly determined. Outside the prison or similar institutional settings, a life devoted to malingering is sufficiently deviant to raise major psychiatric questions.