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Junk Science & Statistics
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| "The first-time availability of prevalence information on personality disorders at the national level is critically important," said Dr. Ting-Kai Li, M.D., Director, National Institute on Alcohol Abuse and Alcoholism.
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| Since Grant conducted the study among a randomly selected population-based sample, the prevalence rates from her study diverged from those presented in the DSM-IV-TR in some cases.
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| For instance, according to the DSM-IV-TR, dependent personality disorder is "among the most frequently reported personality disorders encountered in mental health clinics," the study report pointed out. However, Grant's study found it to be the least common in the population.
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| In addition, the DSM-IV-TR estimates that the prevalence of avoidant personality disorder in the general population is between 0.5 percent and 1 percent, yet Grant found it to be 2.36 percent.
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| Grant explained that prevalence estimates of various personality disorders in the DSM are based on relatively small, clinical studies of patients who are receiving mental health services on an inpatient or outpatient basis.
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| "You can run into problems if you rely solely on clinical samples," she said. "If you want to know the true prevalence of a certain disorder, you have to get out of the clinic."
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| For example, 25 to 85 percent of people diagnosed with one personality disorder also meet the criteria for another one (Widiger & Rogers, 1989; Zimmerman & Coryell, 1989). In terms of Axis I comorbidity, anywhere from 27 to 65 percent of patients with panic disorder or generalized anxiety disorder show a coexisting personality disorder (Brown & Barlow, 1992). Because of this comorbidity, it is often difficult to determine whether a client suffers two or more disorders or whether the problems attributed to an Axis I condition are actually the result of a pervasive personality disorder.
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| The prevalence of personality disorders in the United States is difficult to estimate, in part because many people with these disorders refuse to acknowledge their problems and avoid contact with clinicians. Another complication stems from the fact that the diagnosis of a personality disorder requires establishing a chronic pattern of problems, which is usually more difficult than diagnosing the acute symptoms of an Axis I disorder.
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| By placing personality disorders on Axis II, the DSM-IV encourages clinicians to diagnose personality disorders in addition to any Axis I disorders that are present. However, clinicians often find it difficult to distinguish Axis I and Axis II disorders, and they are uncertain how best to think about clients with diagnoses on both axes.
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| Comorbidity between Axis I and Axis II disorders can be understood in several ways (Klein, 1993). First, an Axis I disorder and a personality disorder may simply coexist at the same time....It is also possible that one of the disorders predisposes a person to develop the other. ...Another interpretation of comorbidity is that it is an artifact of the criteria used for various diagnoses. ...For example, Comorbidity may simply be the result of definitional similarity. ...A personality disorder and an Axis I disorder may represent different levels of severity along the same basic dimensions of disturbance.
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| At least three other problems make reliable diagnosis of personality disorders difficult. First, as suggested in the discussion of comorbidity, the criteria used to define different personality disorders often overlap considerably. ...A second obstacle to reliable diagnosis of personality disorders is that, by definition, they refer to long-standing behavior patterns rather than acute, current symptoms....Finally, the problems associated with the DSMIV's categorical approach to classification are particularly difficult in the case of personality disorders. As noted in Chapter 2, the DSM-IV requires the clinician to assign a diagnosis if a client meets a particular number out of a fixed set of criteria. If this number is met (for example, five out of nine for narcissistic personality disorder) the diagnosis is made. But there is little or no evidence to support a particular cutoff (such as five of nine instead of six of nine criteria) as being the "true" boundary between normal and abnormal personality (Widiger & Trull, 1991). Furthermore, if the rule requires that five of nine criteria be met, two people could be diagnosed as displaying narcissistic personality disorders even though they share only one defining feature. And two other people who share four defining features might receive different diagnoses because they do not share a fifth criterion.
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| Histrionic personality disorder occurs in about 2 to 4 percent of the U.S. population (Weissman, 1993), and it appears to be diagnosed more often in females than in males. The reasons for this gender difference remain controversial. It may reflect cultural influences that lead females, especially, to believe that physical beauty is necessary for a satisfying life, or it may be due to the diagnostic biases described in Chapter 2. Recall the study by Maureen Ford and Tom Widiger in which clinicians were asked to diagnose fictitious cases. One case involved a typical description of antisocial personality disorder for which the person was said to be either a man or a woman; the other described a histrionic personality disorder, again presented as either a man or woman. The results showed that clinicians were more likely to diagnose a female with histrionic personality disorder even when she met the criteria for antisocial personality disorder. Likewise, histrionic behavior attributed to a female increased clinicians' use of the histrionic diagnosis. On the other hand, being identified as a male had a smaller effect on the differential use of the two diagnoses. Researchers' interest in histrionic personality disorder appears to have declined recently; it may be diagnosed less frequently in the future since it overlaps considerably with other personality disorders in the dramatic/emotional/erratic cluster.
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| The high preponderance of male patients in studies of narcissism has prompted researchers to explore the effects of gender roles on this particular personality disorder. Some have speculated that the gender imbalance in NPD results from society's disapproval of self-centered and exploitative behavior in women, who are typically socialized to nurture, please, and generally focus their attention on others. Others have remarked that the imbalance is more apparent than real, and that it reflects a basically sexist definition of narcissism. These researchers suggest that definitions of the disorder should be rewritten in future editions of DSM to account for ways in which narcissistic personality traits manifest differently in men and in women.
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