Tripartite Model of Psychopathology
Three-part model consisting of general distress, anxious arousal, and anhedonia, created to explain both (a) the symptom overlap and comorbidity and (b) the differentiation between anxiety and depression.
The tripartite model consists of three components: a shared general distress factor and specific factors for anxiety and depression. The shared general distress factor is primarily characterized by negative affectivity, the tendency to be temperamentally sensitive to negative stimuli (Clark et al. 1994). The specific factor for anxiety is defined by anxious arousal that is primarily characterized by symptoms of physical hyperarousal, such as racing heart, shortness of breath, and dizziness (Clark et al. 1994). The specific factor for anhedonia is defined by low positive affectivity, the inability to feel positive emotions such as joyfulness, enthusiasm, and assertiveness (Clark et al. 1994).
Shared General Factor
In order to determine the extent to which empirical findings support the existence of mixed mood disorders, Clark and Watson (1991a) conducted a meta-analysis on psychometric data relevant to mixed anxiety-depression. In this meta-analysis, Clark and Watson (1991a) investigated the convergent and discriminant validity of the most commonly used measures of mood states, as well as anxious and depressive symptom measures, using data from both patient and nonpatient samples. Indicators of anxiety and depression (both mood measures and symptoms) displayed strong convergent validity, suggesting that the various scales were targeting the same constructs. In terms of discriminant validity, Clark and Watson (1991a) found high correlations between the anxiety scales and the depression scales, suggesting that there is low specificity in their measurement. Taken together, the convergent and discriminant validity data suggest that there is a large nonspecific component shared by both syndromes.
Specific Factors in Depression and Anxiety
Clark and Watson (1991b) determined the existence of specific components in depression and anxiety through a factor analysis of 10 of the most commonly used anxiety and depression scales at the time. The first factor, primarily represented by the Beck Depression Inventory (BDI) and the Minnesota Multiphasic Personality Inventory (MMPI) anxiety scales, was characterized by general negative affectivity. The second factor, primarily represented by the Costello-Comrey Anxiety scale, was characterized by fearful mood, anxious vigilance, and motor tension. There was an absence of a specific depression factor, though it was hypothesized that this was due to there being insufficient items tapping this particular content.
Within the same study, Clark and Watson (1991b) reviewed a number of studies that directly factor analyzed general neurotic symptoms and identified separate anxiety and depression factors. These data supported a tripartite division of depression and anxiety into (a) a general neuroticism factor, which was characterized by feelings of inferiority and rejection, oversensitivity to criticism, self-consciousness, and social distress; (b) a specific anxiety factor (termed anxious arousal) that was characterized by somatic symptoms, such as feelings of tension, nervousness, shakiness, and panic; and (c) a specific depression factor (termed anhedonia) that was characterized by indicators of low positive affect, such as loss of interest or pleasure, anorexia, crying spells, hopelessness, loneliness, and, sometimes, suicidal ideation.
Based on the results of these studies, Clark and Watson (1991a) suggested that elevated levels of general distress signal the presence of either anxiety or depression, but do not offer any discrimination between the two conditions. An additional elevation in anhedonia suggests the presence of depression, whereas elevation in anxious arousal suggests the presence of anxiety. Clark and Watson (1991a) also proposed the existence of a mixed mood disorder, which is characterized by either relatively high or low levels of both anhedonia and anxious arousal.
Measurement of the Tripartite Model
In order to test the tripartite model, Watson and Clark (1991a) created the Mood and Anxiety Symptom Questionnaire (MASQ). The MASQ is a rationally derived instrument containing a range of symptoms relevant to both depression and anxiety. The initial instrument consisted of five scales: (1) General Distress: Anxious Symptoms (GD: Anxiety), which contained nonspecific symptoms included within the DSM anxiety disorders; (2) General Distress: Depressive Symptoms (GD: Depression), which included nonspecific symptoms found within the mood (depressive) disorders; (3) General Distress: Mixed Symptoms (GD: Mixed), which assessed nonspecific symptoms found within both the mood and anxiety disorders; (4) Anhedonic Depression, which was designed to assess low positive affect; (5) and Anxious Arousal, which contained symptoms of somatic hyperarousal.
In a later study testing the tripartite model across five samples (including students, adults, and patients), Watson et al. (1995b) found poor discriminant validity between the different general distress scales but good discriminant validity between the Anxious Arousal and Anhedonic Depression scales. These results support the tripartite model, which stated that general distress is shared by anxiety and depression (thereby producing poor discriminant validity between the three general distress scales), whereas the specific factors of anxiety and depression are distinct from one another. Consistent with the tripartite model, the MASQ Anxious Arousal and Anhedonic Depression scales also displayed good convergent validity with other indicators of anxiety and depression, respectively. Taken together, these results highlight an important prediction in Clark and Watson’s (1991a) tripartite model: In order to differentiate anxiety and depression, one should focus on the specific factors rather than the shared dimension of general distress/negative affectivity.
In a follow-up study, Watson et al. (1995a) conducted separate factor analyses of the 90 MASQ items in the same five samples. Three robust factors – general distress, anxious arousal, and anhedonia versus positive affect – emerged in each of the five samples. Watson et al. (1995a) found that although the hypothesized three-factor structure was replicated and most of the MASQ items were correctly placed, some of the items did not perform as expected. For example, the specific anxiety factor that emerged was defined by a broad range of somatic symptoms, including some that do not clearly reflect autonomic hyperarousal (e.g., nausea, diarrhea). Taking both studies together, these data suggest that the tripartite model is highly valid across a diverse range of participants.
Replication of the Tripartite Model
Joiner et al. (1996) factor analyzed the items from the Children’s Depression Inventory (CDI) and the Revised Children’s Manifest Anxiety Scale (RCMAS) in a sample of 116 child and adolescent psychiatric inpatients. They obtained a three-factor solution consisting of the tripartite model dimensions, thereby replicating the model in a child and adolescent sample.
Criticism of the Tripartite Model
Anxiety disorders are extremely heterogeneous and consist of a diverse range of symptoms. Individual anxiety disorders relate differently to depression, with some disorders having more overlap with it than others. Therefore, the single anxious arousal factor of the tripartite model is insufficient to fully account for the broad range of symptoms subsumed by the anxiety disorders (Brown et al. 1998). Accordingly, Mineka et al. (1998) proposed an integrative hierarchical model of anxiety and depression. According to the integrative hierarchical model, each individual anxiety disorder contains both a common and unique component. In this revised model, anxious arousal is no longer viewed as the specific component of all anxiety disorders, but plays a more limited role as the specific component of panic disorder.
The tripartite model consists of three symptom components: a shared general distress component and specific factors of anxiety (anxious arousal) and depression (anhedonia). The tripartite model has been replicated across a broad range of young adult and older adult samples, as well as child and adolescent psychiatric samples. However, the tripartite model’s anxious arousal component has been criticized as being too narrow to fully explain the broad range of anxiety disorder symptoms and has been shown to be most relevant to panic disorder. In response to this criticism, the subsequent integrative hierarchical model of anxiety and depression was proposed.
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