Toward a Comprehensive Symptom-Based Model of Psychopathology

This chapter reviews major findings reported in earlier chapters. First, previous findings confirm the existence of specific symptom dimensions that are highly robust and that show strong convergent and discriminant validity. Second, they establish the existence of multiple symptom dimensions within several disorders. Third, they demonstrate that these specific symptom dimensions have differential criterion validity, differential diagnostic specificity, and differential incremental validity. These symptom data can be used to improve various DSM diagnoses, such as major depression and posttraumatic stress disorder. More fundamentally, they provide the basis for a comprehensive symptom-based model of psychopathology. In addition to the IDAS-II, other instruments assess dimensions underlying sleep disorders, eating disorders, schizotypy, personality disorder, and hypochondriasis. These instruments jointly provide broad coverage of the 19 diagnostic classes contained in DSM-5. These measures support movement away from disorder-based models of psychopathology to ones focused on homogeneous symptom dimensions.

The Structure, Specificity, and Validity of Depression Symptoms

This chapter examines key symptom criteria of major depression. It begins by developing a comprehensive measurement model based on six symptom dimensions: dysphoria, lassitude, insomnia, suicidality, appetite loss, and appetite gain. It then demonstrates that these symptom dimensions are robust and show impressive convergent and discriminant validity across multiple methods (self-reports, clinicians’ ratings, interview assessments). Three types of symptoms—dysphoria, lassitude, and suicidality—exhibit strong criterion validity and significant specificity in relation to diagnoses of major depression. In contrast, symptoms of insomnia and appetite disturbance display unimpressive criterion validity and poor specificity. Moreover, these nonspecific symptoms provided little or no incremental information in logistic regression analyses. Taken together, these results suggest that the diagnosis of depression can be improved by focusing primarily on strong and specific symptoms (such as dysphoria and lassitude) and deemphasizing weak and nonspecific symptoms (i.e., insomnia and appetite disturbance).

The Structure, Validity, and Specificity of OCD Symptoms

This chapter reviews early attempts to assess obsessive-compulsive disorder (OCD) symptoms, as well as the structural evidence that eventually led to the identification of core, consensual dimensions within the disorder. It then reviews instruments (the Obsessive-Compulsive Inventory; the Schedule of Compulsions, Obsessions, and Pathological Impulses; and the Yale-Brown Obsessive-Compulsive Scale) that have been developed to assess these core symptom dimensions and discusses the validity (including convergent, discriminant, criterion, and incremental validity) and specificity of the scales included in these measures. Three sets of OCD-related items (representing Cleaning, Checking, and Ordering) marked clear, replicable factors in the IDAS-II scale development samples. Indicators of checking and ordering/rituals produced the most impressive results overall, exhibiting the strongest criterion validity, good diagnostic specificity, and significant incremental validity in logistic regression analyses. Washing/cleaning symptoms also showed good diagnostic specificity, but they displayed more moderate criterion validity.

Anxiety Symptoms

This chapter reviews the convergent, discriminant, criterion, and incremental validity of symptoms of the DSM-5 anxiety disorders; these include panic disorder, agoraphobia, social anxiety disorder/social phobia, specific phobia, and generalized anxiety disorder (GAD). Symptom measures of social anxiety/social phobia, panic disorder, claustrophobia, and GAD generally displayed impressive construct validity in these data. Specifically, they tended to show strong convergent validity and significant discriminant validity across both self-report and interview-based measures; moreover, they displayed substantial criterion validity and impressive incremental validity in relation to conceptually linked DSM diagnoses. One problem, however, is that they generally showed poor diagnostic specificity; that is, although they correlated substantially with their target diagnoses, they often displayed equally strong relations with at least some other internalizing disorders. In contrast, self-report measures of agoraphobia and specific phobia (particularly the latter) generally exhibited unimpressive criterion and incremental validity in these analyses.

Positive Mood Dysfunction in Psychopathology

This chapter explores the nature of positive emotional disturbance across various disorders. It reviews findings based on the positive affect scales of the Expanded Form of the Inventory of Depression and Anxiety Symptoms (IDAS-II), the Clinician Rating version of the IDAS (IDAS-CR), and the Expanded Form of the Positive and Negative Affect Schedule (PANAS-X). These data reveal that IDAS-II Well-Being, IDAS-CR Well-Being, and PANAS-X Joviality assess a highly adaptive form of positive affect. These measures show particularly strong negative associations with symptoms and diagnoses of depression; they also are negatively related to social anxiety and to the negative symptoms (aloofness, restricted affectivity) of psychosis. In contrast, IDAS-II Euphoria and PANAS-X Self-Assurance tap a more dysfunctional form of positive affect. These scales correlate positively with many forms of psychopathology, including mania, narcissism, histrionic personality disorder, and the positive symptoms of psychosis (e.g., eccentricity, unusual beliefs and experiences).

Anger and Psychopathology

This chapter explores how individual differences in anger and hostility are linked to a broad range of psychopathology. An examination of this topic is complicated by the fact that measures of anger/hostility correlate strongly with other types of negative affect, such as fear/anxiety and sadness/depression; it therefore is important to control for the influence of these other negatively valenced emotions when examining relations with psychopathology. The reviewed data indicate that anger/hostility scales tend to show weak to moderate associations with internalizing psychopathology; however, these relations essentially disappear after controlling for other types of negative affect. In contrast, anger/hostility displays somewhat stronger associations with externalizing that remain significant after controlling for anxiety and depression. Finally, anger/hostility scales exhibit relatively strong and specific relations with paranoia/suspiciousness and social anhedonia/withdrawal—which persist after controlling for the other negative emotions—but are not consistently linked to other forms of psychoticism.

The Underlying Nature and Structure of the Emotional Disorders

This chapter examines the nature and structure of the emotional disorders, which include five adjacent diagnostic classes within the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders: bipolar and related disorders, depressive disorders, anxiety disorders, obsessive-compulsive and related disorders, and trauma- and stressor-related disorders. It reviews the pervasive problem of comorbidity—that is, the co-occurrence of two or more disorders within the same person—that characterizes these disorders, and it discusses several influential models (including the tripartite model and the integrative hierarchical model) that have been developed to account for these data. It then examines several problems associated with diagnosis-based approaches to psychopathology; these include hierarchical exclusion rules, low prevalence rates, diagnostic unreliability, and the heterogeneity of many disorders. Finally, it proposes an alternative approach to studying psychopathology, namely, examining the specific symptom dimensions that make up the major syndromes within the emotional disorders.

The Structure, Validity, and Specificity of PTSD Symptoms

This chapter explicates the properties of posttraumatic stress disorder (PTSD) symptoms. It focuses on four basic types of PTSD symptoms: intrusions/reexperiencing, avoidance, hyperarousal, and dysphoria/numbing. Indicators of intrusions/reexperiencing showed the strongest overall criterion validity and impressive diagnostic specificity vis-à-vis PTSD diagnoses; they also displayed significant incremental predictive power in logistic regression analyses. Avoidance symptoms behaved similarly and also appear to have a relatively strong and specific association with PTSD diagnoses. The data for hyperarousal symptoms were more mixed: They tended to exhibit moderate to strong criterion validity, with inconsistent evidence of diagnostic specificity and incremental validity. Finally, although dysphoria/numbing symptoms displayed some criterion validity, they actually showed diagnostic specificity to major depression—not PTSD—and demonstrated virtually no incremental predictive power in the logistic regression analyses. Thus, these symptoms were neither specific to PTSD nor necessary in predicting the diagnosis.

Development of the IDAS and IDAS-II

This chapter describes the creation of an instrument providing comprehensive assessment of emotional disorder symptoms. The original Inventory of Depression and Anxiety Symptoms (IDAS) was created to address limitations associated with older measures of these disorders. The original IDAS contained symptom scales assessing depression (General Depression, Dysphoria, Suicidality, Lassitude, Insomnia, Appetite Loss, Appetite Gain), anxiety (Panic, Social Anxiety, Traumatic Intrusions), anger (Ill Temper), and positive mood (Well-Being). The Expanded Form of the IDAS (IDAS-II) subsequently was created to provide additional coverage of anxiety (Claustrophobia, Traumatic Avoidance), obsessive-compulsive (Checking, Ordering, Cleaning), and bipolar (Mania, Euphoria) symptoms. The IDAS-II scales are internally consistent and stable over short time intervals. Most scales show substantial elevations in clinical samples. Structural analyses of the IDAS-II scales reveal three underlying factors: distress, obsessions/fear, and positive mood. Finally, nationally representative norms are presented for the IDAS-II scales.

The Nature and Structure of Bipolar Symptoms

This chapter reviews key properties of mania symptoms. These symptoms are unusual in that they tend to be associated with elevated levels of both distress/negative emotionality and energy/positive emotionality. It is noteworthy, moreover, that individual symptom measures assess these two components to varying degrees, such that some place greater weight on elevated negative emotionality, whereas others focus more on excessive positive emotionality. In fact, structural analyses of mania symptom measures reveal two underlying dimensions. First, Manic Distress taps individual differences in affective lability, restlessness, and cognitive manifestations of mania (e.g., pressure of speech). Scores on this factor correlate substantially with neuroticism and negative affectivity. Second, Manic Elation reflects individual differences in elation, excitement, and energy/activation; this factor correlates strongly with scales assessing extraversion and positive emotionality. The identification of these distinct factors has important implications for the conceptualization and assessment of bipolar disorder.