The Effect of Causal Theories on Mental Disorder Diagnosis.

The well-documented idea that categorization processes are driven in part by theory-like category representations contrasts sharply with the atheoretical approach to mental disorder diagnosis taken by the Diagnostic and Statistical Manual of Mental Disorders (4 Ed., American Psychological Association, 1994). The current paper reviews recent findings showing that clinical psychologists, lacking specification of theories by the DSM, instead hold their own personal theories about how the symptoms of mental disorders are causally related to each other. Furthermore, these personal theories markedly influence how clinicians perceive, diagnose, and remember their patients. We discuss the implications of these results for the atheoretical DSM system, as well as the rationality of being influenced by theories. Causal theories and diagnosis, 3 The Effect of Causal Theories on Mental Disorder Diagnosis One of the most ubiquitous findings in cognitive psychology is that of top-down processing. Namely, people’s expectations can influence their perception (e.g., Cavanagh, 1999), categorization (e.g., Murphy & Medin, 1985), memory (e.g., Mather, Johnson, & DeLeonardis, 1999), attention (e.g., Itti, Braun, & Koch, 2002), and so on. Such expectations may be elicited by anything ranging from cues in the surrounding context to the beliefs and theories that the person brings to the situation. In recent years, the lion’s share of research has been devoted to documenting the effects of people’s existing beliefs, knowledge, and domain theories on a wide range of cognitive tasks (e.g., Lin & Murphy, 1997; Rehder & Hastie, 2001; Wellman, 1990). Mental disorder diagnosis poses a particularly interesting case because the Diagnostic and Statistical Manual of Mental Disorders (4 Ed., American Psychiatric Association, 1994) establishes a set of atheoretical guidelines. This paper reviews a series of recent studies demonstrating that clinical psychologists are cognitively driven to apply their causal theories about mental disorders when reasoning about them, despite decades of training and practice with the DSM’s atheoretical guidelines. Evolution of the DSM In 1952, the American Psychiatric Association published the first edition of the Diagnostic and Statistical Manual of Mental Disorders. At that time, psychoanalysis was a highly influential philosophy, with at least 10 out of 28 members of the committee being members of psychoanalytic organizations or sympathetic to that approach (Shorter, 1997). In view of this fact, it is not difficult to find influences of psychoanalytic theory in the DSM-I (APA, 1952). In 1968, the second edition of the Diagnostic and Statistical Causal theories and diagnosis, 4 Manual appeared. Again, psychoanalysis heavily influenced the development of this edition, as reflected by the fact that 6 of the 10 members of the drafting committee were analysts or belonged to sympathetic organizations (Shorter, 1997). Freudian theoretical terms such as “neuroses” and “hysteria” freely appeared, where hysteria referred to symptoms associated with “emotionally charged situations” that are “symbolic of the underlying conflicts” (APA, 1968, p. 39). However, these theoretical constructs offered few operational criteria needed for reliable diagnoses (e.g., Hempel, 1965). Furthermore, by the early 1970’s, psychoanalysis was not the only predominant philosophy, making it difficult for the DSM-II (APA, 1968) to be accepted by clinicians taking different theoretical orientations. In addition to this complication, most mental disorders still lacked a single universally acknowledged pathogenesis. In response to these problems, the later editions of the DSM (i.e., DSM-III, 1980; DSM-III-R, 1988; DSM-IV, 1994) took a radically different approach; namely, “a descriptive approach that attempted to be neutral with respect to theories of etiology” (APA, 1994; pp. xvii-xviii). In accord with this theory-neutral approach, most disorders are defined in terms of a set of surface symptoms or conditions the patient must meet for diagnosis. For example, schizophrenia is characterized by 5 symptoms (hallucinations, delusions, disorganized speech, grossly disorganized or catatonic behavior, and negative symptoms). Clinicians are to search for symptoms in their patients that match the DSMIV (APA, 1994) diagnostic criteria, without incorporating any additional notions they may have of how these symptoms may affect each other and, in most disorders, what caused these symptoms in the first place. Causal theories and diagnosis, 5 Another significant shift in the assumptions underlying the representation of mental disorders is that starting from the DSM-III, a probabilistic model has been explicitly adopted. According to this model, boundaries of categories are fuzzy and categories do not necessarily have defining features. For example, the prototypical patient with Schizophrenia has five symptoms, but a presenting patient need only have two of those five symptoms for a diagnosis of the disorder. In some sense, this is a natural consequence of taking the atheoretical symptom-based approach, because although patients with the same disorder might share a common underlying cause, the manifestations at the symptomatic level might vary depending on individual patients’ genetic tendencies and/or life experiences. The Atheoretical Nature of the DSM-IV Over the past 20 years beginning with the DSM-III (APA, 1980), the DSM system has been positioned at the core of research, diagnosis, and treatment in psychopathology in the U.S. As Joiner and Schmidt (2002) put it, “It is perhaps only a slight overstatement to say that one cannot get paid – either by insurance or granting agencies – unless DSM diagnoses are assigned” (p. 107). Given that the DSM is so important in clinicians’ professional lives, has the DSM’s atheoretical stance been internalized by clinicians? A series of earlier studies by Cantor and her colleagues presented evidence suggest! ing that clinicians appear to represent mental disorders in a way similar to the recent atheoretical DSM systems; that is, in terms of prototypes. In Cantor, Smith, French, and Mezzich (1980), for instance, atypical patients sharing only a small number of symptoms with disorder prototypes were diagnosed less accurately and confidently than typical patients sharing a large number of symptoms with disorder prototypes. This Causal theories and diagnosis, 6 phenomenon, known as the typicality effect, has been ubiquitously observed in natural categorization. Just to name a few, people are faster at judging a robin as a bird than judging a chicken as a bird, people generate typical members before atypical ones in generating exemplars of a category, and so on (see Smith & Medin, 1981 for a review). Citing such evidence, the prototype approach to categorization posits that people store prototypes of categories that are usually represented in terms of surface features (e.g., “have wings,” “fly,” “build nests,” for birds), and that the categorization of a new object is determined by its similarity to the stored prototypical representation. According to the prototype view, typicality effects arise due to variance in this similarity. However, the fact that typicality effects occur does not necessarily mean that people represent categories only in terms of surface features or that categorization is solely based on surface similarity. For instance, our concept of birds is not just a list of bird features; most people know that birds can fly because they have wings, and birds can build nests i! n trees because they can fly. More generally speaking, even lay people’s concepts are akin to scientific theories, albeit naïve (e.g., Murphy & Medin, 1985; Keil, 1989; Carey, 1985; See Ahn, Marsh, Luhmann, & Lee, 2002, for examples of lay people’s theories about natural categories). In the domain of mental disorders, Kim and Ahn (2002-b) found that lay people’s concept of anorexia, for instance, not only contains the features "fear of becoming fat" and "refuses to maintain minimal body weight," but also the notion that the fear of becoming fat helps cause the refusal to maintain minimal body weight. These findings support Medin’s (1989) suggestion in American Psychologist that the DSM system, which represents mental disorders simply as lists of independent symptoms, "provides only a skeletal outline that is brought to life by theories Causal theories and diagnosis, 7 and causal scenarios underlying and intertwined with the symptoms that comprise the diagnostic criteria (p. 1479). ” In what follows, we will first review evidence showing that clinicians’ representations of mental disorders are not in fact lists of independent symptoms, but rather consist of theory-like structures connecting these symptoms. Afterwards, we will discuss the specific effects of these theories on clinicians’ reasoning. First, we will examine how clinicians’ theories determine which symptoms are perceived as more central or important than others are. Second, we will discuss how causal relations among symptoms influence clinicians’ overall perception of how normal or abnormal patients are. Along the way, we will also contrast these findings with lay people’s theories and the influence of those theories on reasoning. Finally, we will discuss whether being influenced by theories is rational. Clinicians Represent Mental Disorders Like Theories Across three experiments, Kim and Ahn (2002-a) presented 35 expert clinical psychologists and 25 novice clinical trainees with lists of the symptoms of ! nine mental disorders and asked them to specify the relations among the symptoms within each disorder. In these studies, Kim and Ahn examined five mental disorders that were prejudged to be highly familiar even to undergraduates (Anorexia nervosa, Schizophrenia, Major depressive episode, Antisocial personality disorder, and Specific phobia) in their Experiments 1 and 2, and four pers