What is one limitation of linnaeus classification system

Chapter 1 Issues in Diagnosis

Conceptual Issues and Controversies

SCOTT O. LILIENFELD, SARAH FRANCIS SMITH, AND ASHLEY L. WATTS

Psychiatric diagnosis is fundamental to the understanding of mental illness. Without it, the study, assessment, and treatment of psychopathology would be in disarray. In this chapter, we examine (a) the raison d’etre underlying psychiatric diagnosis, ˆ (b) widespread misconceptions regarding psychiatric diagnosis, (c) the present system of psychiatric diagnosis and its strengths and weaknesses, and (d) fruitful directions for improving this system. A myriad of forms of abnormality are housed under the exceedingly broad umbrella of mental disorders. Indeed, the current psychiatric classification system contains well over 300 diagnoses (American Psychiatric Association [APA], 2013). The enormous heterogeneity of psychopathology makes a formal system of organization imperative. Just as in the biological sciences, where Linnaeus’ hierarchical taxonomy categorizes fauna and flora, and in chemistry, where Mendeleev’s periodic table orders the elements, a psychiatric classification system helps to organize the bewildering subforms of abnormality. Such a system, if effective, permits us to parse the variegated universe of psychological disorders into more homogeneous, and ideally more clinically meaningful, categories. From the practitioner’s initial inchoate impression that a patient’s behavior is aberrant to later and better-elaborated case conceptualization, diagnosis plays an integral role in the clinical process. Indeed, the essential reason for initiating assessment and treatment is often the observer’s sense that “something is just not quite right” about the person. Meehl (1973) commented that the mental health professional’s core task is to answer the question: “What does this person have, or what befell him, that makes him different from those who have not developed clinical psychopathology?” (p. 248). Therein lies the basis for psychiatric diagnosis. General Terminological Issues Before proceeding, a bit of terminology is in order. It is crucial at the outset to distinguish two frequently confused terms: classification and diagnosis. A system of classification is an overarching taxonomy of mental illness, whereas diagnosis is the act of placing an individual, based on a constellation of signs (observable indicators, like crying in a 1 Craighead, W. E. (2013). Psychopathology : history, diagnosis, and empirical foundations. Retrieved from http://ebookcentral.proquest.com Created from ashford-ebooks on 2017-10-10 13:48:20. Copyright © 2013. John Wiley & Sons, Incorporated. All rights reserved. 2 ISSUES IN DIAGNOSIS depressed patient), symptoms (subjective indicators, like feelings of guilt in a depressed patient), or both, into a category within that taxonomy. Classification is a prerequisite for diagnosis. Another key set of terminological issues concerns the distinctions among syndrome, disorder, and disease. As Kazdin (1983) observed, we can differentiate among these three concepts based on our levels of understanding of their pathology—the underlying physiological changes that may accompany the condition—and etiology, that is, causation (Gough, 1971; Lilienfeld, Waldman, & Israel, 1994). At the lowest rung of the hierarchy of understanding there are syndromes, which are typically constellations of signs and symptoms that co-occur across individuals (syndrome means “running together” in Greek). In syndromes, neither pathology nor etiology is well understood, nor is the syndrome’s causal relation to other conditions established. Antisocial personality disorder is a relatively clear example of a syndrome because its signs (e.g., the use of an alias) and symptoms (e.g., lack of remorse) tend to covary across individuals. Nevertheless, its pathology and etiology are largely unknown, and its causal relation to other conditions is poorly understood (Lykken, 1995). In contrast, some authors (e.g., Lilienfeld, 2013; but see Lynam & Miller, 2012) argue that psychopathic personality (psychopathy) may not be a classical syndrome. These researchers contend that psychopathy is instead a configuration of several largely independent constructs, such as boldness, coldness, and disinhibition, that come together in an interpersonally malignant fashion (Patrick, Fowles, & Krueger, 2009; see also Vitale & Newman, Chapter 16, this book). In other cases, syndromes may also constitute groupings of signs and symptoms that exhibit minimal covariation across individuals but that point to an underlying etiology (Lilienfeld et al., 1994). For example, Gerstmann’s syndrome in neurology (Benton, 1992) is marked by four major features: agraphia (inability to write), acalculia (inability to perform mental computation), finger agnosia (inability to differentiate among fingers on the hand), and left-right disorientation. Although these indicators are negligibly correlated across individuals in the general population, they co-occur dependably following certain instances of parietal lobe damage. At the second rung of the hierarchy of understanding there are disorders, which are syndromes that cannot be readily explained by other conditions. For example, in the present diagnostic system, obsessive-compulsive disorder (OCD) can be diagnosed only if its symptoms (e.g., recurrent fears of contamination) and signs (e.g., recurrent hand washing) cannot be accounted for by a specific phobia (e.g., irrational fear of dirt). Once we rule out other potential causes of OCD symptoms, such as specific phobia, anorexia nervosa, and trichotillomania (compulsive hair pulling) we can be reasonably certain that an individual exhibiting marked obsessions, compulsions, or both, suffers from a well-defined disorder (APA, 2000, p. 463). At the third and highest rung of the hierarchy of understanding there are diseases, which are disorders in which pathology and etiology are reasonably well understood (Kazdin, 1983; McHugh & Slavney, 1998). Sickle-cell anemia is a prototypical disease because its pathology (crescent-shaped erythrocytes containing hemoglobin S) and etiology (two autosomal recessive alleles) have been conclusively identified (Sutton, 1980). For other conditions that approach the status of bona fide diseases, such as Alzheimer’s disease, the primary pathology (senile plaques, neurofibrillary tangles, and granulovacuolar degeneration) has been identified, while their etiology is evolving but incomplete (Selkoe, 1992). Craighead, W. E. (2013). Psychopathology : history, diagnosis, and empirical foundations. Retrieved from http://ebookcentral.proquest.com Created from ashford-ebooks on 2017-10-10 13:48:20. Copyright © 2013. John Wiley & Sons, Incorporated. All rights reserved. FUNCTIONS OF PSYCHIATRIC DIAGNOSIS 3 With the possible exception of Alzheimer’s disease and a handful of other organic conditions, the diagnoses in our present system of psychiatric classifications are almost exclusively syndromes or, in rare cases, disorders (Kendell & Jablensky, 2003). This fact is a sobering reminder that the pathology in most cases of psychopathology is largely unknown, and their etiology is poorly understood. Therefore, although we genuflect to hallowed tradition in this chapter by referring to the major entities within the current psychiatric classification system as mental “disorders,” readers should bear in mind that few are disorders in the strict sense of the term. Functions of Psychiatric Diagnosis Diagnosis serves three principal functions for practitioners and researchers alike. We discuss each in turn. DIAGNOSIS AS COMMUNICATION Diagnosis furnishes a convenient vehicle for communication about an individual’s condition. It allows professionals to be reasonably confident that when they use a diagnosis (such as dysthymic disorder) to describe a patient, other professionals will recognize it as referring to the same condition. Moreover, a diagnosis (such as borderline personality disorder) distills relevant information, such as frantic efforts to avoid abandonment and chronic feelings of emptiness, in a shorthand form that aids in other professionals’ understanding of a case. Blashfield and Burgess (2007) described this role as “information retrieval.” Just as botanists use the name of a species to summarize distinctive features of a specific plant, psychologists and psychiatrists rely on a diagnosis to summarize distinctive features of a specific mental disorder (Blashfield & Burgess, 2007). Diagnoses succinctly convey important information about a patient to clinicians, investigators, family members, managed care organizations, and others. ESTABLISHING LINKAGES TO OTHER DIAGNOSES Psychiatric diagnoses are organized within the overarching nosological structure of other diagnoses. Nosology is the branch of science that deals with the systematic classification of diseases. Within this system, most diagnostic categories are arranged in relation to other conditions; the nearer in the network two conditions are, the more closely related they ostensibly are as disorders. For example, social anxiety disorder (social phobia) and specific phobia are both classified as anxiety disorders in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5; APA, 2013), and are presumably more closely linked etiologically than are social anxiety disorder and narcissistic personality disorder, the latter of which is classified as a personality disorder in DSM-5. Thus, diagnoses help to locate the patient’s presenting problems within the context of both more and less related diagnostic categories. PROVISION OF SURPLUS INFORMATION Perhaps most important, a diagnosis helps us to learn new things; it affords us surplus information that we did not have previously. Among other things, a diagnosis allows us Craighead, W. E. (2013). Psychopathology : history, diagnosis, and empirical foundations. Retrieved from http://ebookcentral.proquest.com Created from ashford-ebooks on 2017-10-10 13:48:20. Copyright © 2013. John Wiley & Sons, Incorporated. All rights reserved. 4 ISSUES IN DIAGNOSIS to generate predictions regarding case trajectory. As Goodwin and Guze (1996) noted, perhaps hyperbolically, “diagnosis is prognosis” (Kendler, 1980). The diagnostic label of bipolar I disorder describes a distinctive constellation of indicators (e.g., one or more manic or mixed episodes) that discriminates the course, rate of recovery, and treatment response from such related conditions as major depression and bipolar II disorder, the latter of which is marked by one or more episodes of hypomania and disabling depression. But a valid diagnosis does considerably more than predict prognosis. Robins and Guze’s (1970) landmark article delineated formal criteria for ascertaining whether a diagnosis is valid. Validity refers to the extent to which a diagnosis measures what it purports to measure. More colloquially, validity is truth in advertising: A valid diagnosis is true to its name in that it correlates in expected directions with external criteria. Specifically, Robins and Guze outlined four requirements for the validity of psychiatric diagnoses. According to them, a valid diagnosis offers information regarding: 1. Clinical description, including symptomatology, demographics, precipitants, and differences from seemingly related disorders. The last-named task of distinguishing a diagnosis from similar diagnoses is called differential diagnosis. 2. Laboratory research, including data from psychological, biological, and laboratory tests. 3. Natural history, including course and outcome. 4. Family studies, especially studies examining the prevalence of a disorder in the firstdegree relatives of probands—that is, individuals identified as having the diagnosis in question. As a further desideratum, some authors have suggested that a valid diagnosis should ideally be able to predict the individual’s response to treatment (Waldman, Lilienfeld, & Lahey, 1995). Nevertheless, this criterion should probably not be mandatory given that the treatment of a condition bears no necessary implications for its etiology. For example, although both schizophrenia and nausea induced by food poisoning generally respond to psychopharmacological agents that block the action of the neurotransmitter dopamine, these two conditions spring from entirely distinct causal mechanisms. Some authors (e.g., Ross & Pam, 1996) have invoked the felicitous phrase ex juvantibus reasoning (reasoning backward from what works) to describe the error of inferring a disorder’s etiology from its treatment. Headaches, as the hoary example goes, are not caused by a deficiency of aspirin in the bloodstream. There is reasonably strong evidence that many mental disorders fulfill Robins and Guze’s (1970) criteria for validity. When these criteria are met, the diagnosis offers additional information about the patient, information that was not available before this diagnosis was made. For example, if we correctly diagnose a patient with schizophrenia, we have learned that this patient: • Is likely to exhibit psychotic symptoms that are not solely a consequence of a severe mood disturbance. • Has a higher than expected likelihood of exhibiting abnormalities on several laboratory measures, including indices of sustained attention, smooth pursuit eye tracking, and detection of biological motion (Kim, Park, & Blake, 2011). • Has a higher than average probability of having close biological relatives with schizophrenia and schizophrenia-spectrum disorders, such as schizotypal and paranoid personality disorders. Craighead, W. E. (2013). Psychopathology : history, diagnosis, and empirical foundations. Retrieved from http://ebookcentral.proquest.com Created from ashford-ebooks on 2017-10-10 13:48:20. Copyright © 2013. John Wiley & Sons, Incorporated. All rights reserved. FUNCTIONS OF PSYCHIATRIC DIAGNOSIS 5 • Is likely to exhibit a chronic course, with few or no periods of entirely normal functioning, but approximately a 30% chance of overall improvement. • Is likely to respond positively to medications that block the action of dopamine, although this is most likely to be the case for the positive symptoms (e.g., delusions, hallucinations) of the disorder (Subotnick et al., 2011). Andreasen (1995) extended the Robins and Guze (1970) framework to incorporate indicators from molecular genetics, neurochemistry, and functional and structural brain imaging as additional validating indicators for psychiatric diagnoses (Kendell & Jablensky, 2003). Her friendly amendment to the Robins and Guze criteria allows us to use endophenotypic indicators to assist in the validation of a diagnosis. Endophenotypes are typically biomarkers or laboratory indicators, that is, “measurable components unseen by the unaided eye along the pathway between disease and distal genotype” (Gottesman & Gould, 2003, p. 636; Waldman, 2005). They are often contrasted with exophenotypes, the traditional signs and symptoms of a disorder. We can view the process of validating psychiatric diagnoses within the overarching framework of construct validity (Cronbach & Meehl, 1955; Loevinger, 1957; Messick, 1995; but see Borsboom, Cramer, Kievit, Zand Scholten, & Franic, 2009, for a different perspective on construct validity), which refers to the extent to which a measure assesses a hypothesized attribute of individuals. As Morey (1991) noted, psychiatric classification systems are collections of hypothetical constructs; thus, the process of validating psychiatric diagnoses is also a process of construct validation. More broadly, we can conceptualize most or even all psychiatric diagnoses as open concepts (Meehl, 1977, 1990). Open concepts are marked by (a) fuzzy boundaries, (b) a list of indicators (signs and symptoms) that are indefinitely extendable, and (c) an unclear inner nature. Recalling that psychiatric diagnoses are open concepts helps us to avoid the perils of premature reification of diagnostic entities (Faust & Miner, 1986). For example, the present diagnostic criteria for schizophrenia are not isomorphic with the latent construct of schizophrenia; they are merely fallible, albeit somewhat valid, indicators of this construct. Yet, the past few decades have occasionally witnessed a troubling tendency to reify and deify the categories within the current classification system, with some authors regarding them as fixed Platonic essences rather than as rough approximations to the true state of nature (Ghaemi, 2003; Michels, 1984). This error is manifested, for example, when journal or grant reviewers criticize researchers for examining alternative operationalizations of mental disorders that depart from those in the current diagnostic manual (see section Psychiatric Classification from DSM-I to the Present, later in this chapter). It is also manifested by the common error of referring to measures of certain psychiatric conditions as “gold standards” (see Skeem & Cooke, 2010, for a discussion of this tendency in the field of psychopathy), a phrasing that is erroneous in view of the fact that all indicators of psychopathology are at present fallible and provisional. In a classic article, Cronbach and Meehl (1955) adopted from neopositivist philosophers of science the term nomological network to designate the system of lawful relationships conjectured to hold between theoretical entities (states, structures, events, dispositions) and observable indicators. They selected the network metaphor to emphasize the structure of such systems in which the nodes of the network, representing the postulated theoretical entities, are connected by the strands of the network, representing the lawful relationships hypothesized to hold among the entities (Garber & Strassberg, 1991). Craighead, W. E. (2013). Psychopathology : history, diagnosis, and empirical foundations. Retrieved from http://ebookcentral.proquest.com Created from ashford-ebooks on 2017-10-10 13:48:20. Copyright © 2013. John Wiley & Sons, Incorporated. All rights reserved. 6 ISSUES IN DIAGNOSIS For Cronbach and Meehl (1955), construct validation is a progressive and never-ending process of testing the links between hypothesized strands of the nomological network, especially those that connect latent constructs, which include psychiatric diagnoses (e.g., schizophrenia and major depression), to manifest indicators, which include the external criteria (e.g., laboratory tests and family history) laid out by Robins and Guze (1970). The more such construct-to-manifest indicator links are corroborated, the more certain we can be that our conception of the diagnosis in question is accurate. From this perspective, the approach to diagnostic validation outlined by Robins and Guze is merely one specific instantiation of construct validation. One limitation of the Robins and Guze (1970) approach to construct validation is its exclusive emphasis on external validation, that is, the process of ascertaining the construct’s associations with correlates that lie outside of the construct itself. As Skinner (1981, 1986; also Loevinger, 1957) observed, internal validation, ascertaining the construct’s inner structure, is also a key component of construct validation. Internal validation can help investigators to test hypotheses regarding a construct’s homogeneity (versus heterogeneity) and factor structure (Waldman et al., 1995). For example, if analyses suggest that a diagnosis consists of multiple and largely independent subtypes, the validity of the diagnosis would be called into question. Alternatively, factorial validity (i.e., the extent to which the factor structure of a diagnosis comports with theoretical predictions) can inform debates regarding the validity of a diagnosis. For example, factor analyses of attention-deficit/hyperactivity disorder (ADHD) generally support the separation of inattention from impulsivity and hyperactivity, as implied by the DSM criteria for this disorder (Martel, Von Eye, & Nigg, 2010). In summary, valid psychiatric diagnoses serve three primary functions: 1. They summarize distinctive features of a disorder and thereby allow professionals to communicate clearly with one another. 2. They place each diagnosis under the umbrella structure of other diagnoses. This nosological framework links one diagnosis to both more and less related diagnoses. 3. They provide practitioners and researchers with surplus information regarding a diagnosed patient’s clinical profile, laboratory findings, natural history, family history, and possible response to treatment; they may also offer information regarding endophenotypic indicators. Misconceptions Regarding Psychiatric Diagnosis Beginning psychology graduate students and much of the general public hold a plethora of misconceptions regarding psychiatric diagnosis; we examine five such misconceptions here. Doing so will also permit us to introduce a number of key principles of psychiatric diagnosis. As we will discover, refuting each misconception regarding psychiatric diagnosis affirms at least one important principle. MISCONCEPTION #1: MENTAL ILLNESS IS A MYTH The person most closely associated with this position is the late psychiatrist Thomas Szasz (1960), who argued famously for over 40 years that the term mental illness is a false Craighead, W. E. (2013). Psychopathology : history, diagnosis, and empirical foundations. Retrieved from http://ebookcentral.proquest.com Created from ashford-ebooks on 2017-10-10 13:48:20. Copyright © 2013. John Wiley & Sons, Incorporated. All rights reserved. MISCONCEPTIONS REGARDING PSYCHIATRIC DIAGNOSIS 7 and misleading metaphor (Schaler, 2004). For Szasz, individuals whom psychologists and psychiatrists term mentally ill actually suffer from problems in living (that is, difficulties in adjusting their behaviors to the demands of society). Moreover, Szasz contended that mental health professionals often apply the mental illness label to nonconformists who jeopardize the status quo (Sarbin, 1969; Szasz, 1960). This label serves as a convenient justification for forcing maladjusted, malcontented, and maverick members of society to comply with prevailing societal norms. Specifically, Szasz maintained that medical disorders can be clearly recognized by a lesion to the anatomical structure of the body, but that the disorder concept cannot be imported to the mental realm because there is no such lesion to indicate deviation from the norm. According to him only the body can become diseased, so mentally ill people do not suffer from an illness akin to a medical disorder. It is undeniable that psychiatric diagnoses are sometimes misapplied. Nevertheless, this legitimate pragmatic concern must be logically separated from the question of whether the mental illness concept itself exists (Wakefield, 1992). We should recall the logical principle of abusus non tollit usum (abuse does not take away use): Historical and sociological misuses of a concept do not negate its validity. Wakefield (1992) and others (e.g., Kendell, 1975) have observed that the Szaszian argument is problematic on several fronts. Among others, it assumes that medical disorders are in every case traceable to discernible lesions in an anatomical structure, and that all lesions give rise to medical disorders. Yet identifiable lesions cannot be found in certain clear-cut medical diseases—such as trigeminal neuralgia and senile pruritis—and certain identifiable lesions, such as albinism, are not regarded as medical disorders (Kendell, 1975; Wakefield, 1992). Szasz’s assertion that identifiable lesions are essentially synonymous with medical disorders is false; therefore, his corollary argument that mental disorders cannot exist because they are not invariably associated with identifiable lesions is similarly false. MISCONCEPTION #2: PSYCHIATRIC DIAGNOSIS IS MERELY PIGEONHOLING According to this criticism, when we diagnose people with a mental disorder, we deprive them of their uniqueness: We imply that all people within the same diagnostic category are alike in all important respects. To the contrary, a psychiatric diagnosis does nothing of the sort; it implies only that all people with that diagnosis are alike in at least one important way. Psychologists and psychiatrists are well aware that even within a given diagnostic category, such as schizophrenia or bipolar I disorder, people differ dramatically in their race and cultural background, personality traits, interests, and cognitive skills (APA, 2013). MISCONCEPTION #3: PSYCHIATRIC DIAGNOSES ARE UNRELIABLE Reliability refers to the consistency of a diagnosis. As many textbooks in psychometrics remind us, reliability is a prerequisite for validity but not vice versa. Just as a bathroom scale cannot validly measure weight if it yields dramatically different weight estimates for the same person over brief periods of time, a diagnosis cannot validly measure a mental disorder if it yields dramatically different scores on measures of psychopathology across times, situations, and raters. Craighead, W. E. (2013). Psychopathology : history, diagnosis, and empirical foundations. Retrieved from http://ebookcentral.proquest.com Created from ashford-ebooks on 2017-10-10 13:48:20. Copyright © 2013. John Wiley & Sons, Incorporated. All rights reserved. 8 ISSUES IN DIAGNOSIS Because validity is not a prerequisite for reliability, extremely high reliability can exist without validity. A researcher who based diagnoses of schizophrenia on patients’ heights would end up with extremely reliable but entirely invalid diagnoses of schizophrenia. There are three major subtypes of reliability. Contrary to popular (mis)conception, these subtypes are frequently discrepant with one another, so high levels of reliability for one metric do not necessary imply high levels for the others. Test-retest reliability refers to the stability of a diagnosis following a relatively brief time interval, typically about a month. In other words, after a short time lapse, will patients receive the same diagnoses? Note that we wrote brief and short in the previous sentences; marked changes following lengthy time lapses, such as several years, may reflect genuine changes in patient status rather than the measurement error associated with test-retest unreliability. In general, we assess test-retest reliability using either a Pearson correlation coefficient or, more rigorously, an intraclass correlation coefficient. Intraclass correlations tend to provide the most stringent estimates of test-retest reliability because, in contrast to Pearson correlations, they are influenced not merely by the rank ordering and differences among people’s scores, but by their absolute magnitude. Our evaluation of the test-retest reliability of a diagnosis hinges on our conceptualization of the disorder. We should anticipate high test-retest reliability only for diagnoses that are traitlike, such as personality disorders, or that tend to be chronic (long-lasting), such as schizophrenia. In contrast, we should not necessarily anticipate high levels of test-retest reliability for diagnoses that tend to be episodic (intermittent), such as major depression. Internal consistency refers to the extent to which the signs and symptoms comprising a diagnosis hang together—that is, correlate highly with one another. We generally assess internal consistency using such metrics as coefficient alpha (Cronbach, 1951) or the mean interitem correlation. Cronbach’s alpha can overestimate the homogeneity of a diagnosis, however, if this diagnosis contains numerous signs and symptoms, because this statistic is affected by test length (Schmidt, Le, & Ilies, 2003). We should anticipate high levels of internal consistency for most conditions in the current classification system given that most are syndromes, which are typically constellations of signs and symptoms that covary across people. Interrater reliability is the degree to which two or more observers, such as different psychologists or psychiatrists, agree on the diagnosis of a set of individuals. High interrater reliability is a prerequisite for all psychiatric diagnoses, because different observers must agree on the presence or absence of a condition before valid research on that condition can proceed. Many early studies of psychiatric diagnosis operationalized interrater reliability in terms of percentage agreement, that is, the proportion of cases on which two or more raters agree on the presence or absence of a given diagnosis. Nevertheless, measures of percentage agreement tend to overestimate interrater reliability. Here’s why: Imagine two diagnosticians working in a setting (e.g., an outpatient phobia clinic) in which the base rate (prevalence) of the diagnosis of specific phobia is 95%. The finding that they agree with each other on the diagnosis of specific phobia 95% of the time would hardly be impressive and could readily be attributed to chance. As a consequence, most investigators today operationalize interrater reliability in terms of the kappa coefficient, which assesses the degree to which raters agree on a diagnosis after correcting for chance, with chance being the base rate of the disorder in question. Nevertheless, the kappa coefficient often Craighead, W. E. (2013). Psychopathology : history, diagnosis, and empirical foundations. Retrieved from http://ebookcentral.proquest.com Created from ashford-ebooks on 2017-10-10 13:48:20. Copyright © 2013. John Wiley & Sons, Incorporated. All rights reserved. MISCONCEPTIONS REGARDING PSYCHIATRIC DIAGNOSIS 9 provides a conservative estimate of interrater reliability, as the correction for chance sometimes penalizes raters for their independent expertise (Meyer, 1997). Many laypersons and even political pundits believe that psychiatric diagnoses possess low levels of reliability, especially interrater reliability. This perception is probably fueled by high-profile media coverage of dueling expert witnesses in criminal trials in which one expert diagnoses a defendant as schizophrenic, for example, and another diagnoses him as normal. After the widely publicized 1982 trial of John Hinckley, who was acquitted on the basis of insanity for his attempted assassination of then-president Ronald Reagan, political commentator George Will maintained (on national television) that the disagreements among expert witnesses regarding Hinckley’s diagnosis merely bore out what most people already knew: that psychiatric diagnosis is wildly unreliable (Lilienfeld, 1995). Yet there is a straightforward explanation for such disagreement: Given the adversarial nature of our legal system, the prosecution and defense typically go out of their way to find expert witnesses who will support their point of view. This inherently antagonistic arrangement virtually guarantees that the interrater reliabilities of experts in criminal trials will be modest at best. Certainly, the interrater reliability of psychiatric diagnoses is far from perfect. Yet for most major mental disorders, such as schizophrenia, mood disorders, anxiety disorders, and alcohol use disorder (alcoholism), interrater reliabilities are typically about as high— intraclass correlations between raters of 0.8 or above, out of a maximum of 1.0—as those for most well-established medical disorders (Lobbestael, Leurgans, & Arntz, 2011; Matarazzo, 1983). Still, the picture is not entirely rosy. For many personality disorders in particular, interrater reliabilities tend to be considerably lower than for other conditions (Maffei et al., 1997; Zimmerman, 1994), probably because most of these disorders comprise highly inferential constructs (e.g., lack of empathy) that raters find difficult to assess during the course of brief interviews. MISCONCEPTION #4: PSYCHIATRIC DIAGNOSES ARE INVALID From the standpoint of Szasz (1960) and other critics of psychiatric diagnosis (Eysenck, Wakefield, & Friedman, 1983), psychiatric diagnoses are largely useless because they do not provide us with new information. According to them, diagnoses are merely descriptive labels for behaviors we do not like. Millon (1975) proposed a helpful distinction between psychiatric labels and diagnoses; a label simply describes behaviors, whereas a diagnosis helps to explain them. When it comes to a host of informal pop psychology labels, like sexual addiction, Peter Pan syndrome, codependency, shopping disorder, Internet addiction, and road rage disorder, Szasz and his fellow critics probably have a point. Most of these labels merely describe collections of socially problematic behavior and do not provide us with much, if any, new information (McCann, Shindler, & Hammond, 2003). The same may hold for some personality disorders in the current classification system. For example, the diagnosis of dependent personality disorder, which has been retained in DSM-5 (APA, 2013), arguably appears to do little more than describe ways in which people are pathologically dependent on others, such as relying excessively on others for reassurance and expecting others to make everyday life decisions for them. Yet, as we have already seen, many psychiatric diagnoses, such as schizophrenia, bipolar I disorder, and panic disorder, do yield surplus information (Robins & Guze, 1970; Craighead, W. E. (2013). Psychopathology : history, diagnosis, and empirical foundations. Retrieved from http://ebookcentral.proquest.com Created from ashford-ebooks on 2017-10-10 13:48:20. Copyright © 2013.