Research has suggested that depression often occurs following stressful life events (see Monroe & Hadjiyannakis, 2002, for a review). However, individuals can vary widely in their responses to such events. Some may develop severe or long-lasting depression, whereas others do not become depressed at all or may experience mild dysphoria. Several factors have been proposed to explain such individual differences in response to life events. For example, the severity of a given negative life event, the amount of social support an individual receives in the face of a traumatic life event, or individual differences in one's biological constitution or psychological characteristics may all modulate reactivity to stressful events. From a cognitive perspective, the meaning or interpretation individuals give to the life events they experience influences whether or not they become depressed and are vulnerable to recurrent, severe, or long-lasting episodes of depression. Two major cognitive theories of depression, the hopelessness theory (Abramson, Metalsky, & Alloy, 1989; Alloy, Abramson, Metalsky, & Hartlage, 1988) and Beck's theory (Beck, 1967,1987), reflect such vulnerability-stress models, in which variability in individual susceptibility to depression following stressful events is understood in terms of differences in cognitive patterns that affect how those events are interpreted. According to both theories, particular negative cognitive styles increase an individual's likelihood of developing episodes of depression after experiencing a negative life event—specifically, a cognitive-ly mediated subtype of depression (Abramson & Alloy, 1990; Abramson et al., 1989). These theories propose that people who possess "depresso-genic" cognitive styles are vulnerable to depression because they tend to generate interpretations of their experiences that have negative implications for themselves and their futures.
In the hopelessness theory (Abramson et al., 1989), people who exhibit a depressogenic inferential style are hypothesized to be vulnerable to developing episodes of depression, particularly a "hopelessness depression" subtype (HD), when they are exposed to negative life events. This de-pressogenic inferential style is characterized by a tendency to attribute negative life events to stable (likely to persist over time) and global (likely to affect many areas of life) causes, to infer that negative consequences will follow from a current negative event, and to infer that the occurrence of a negative event in one's life means that one is fundamentally flawed or worthless. People who exhibit such an inferential style should be more likely to make negative inferences regarding the causes, consequences, and self-implications of any stressful event they experience, thereby increasing the likelihood that they will develop hopelessness, the proximal sufficient cause of the symptoms of hopelessness depression.
In Beck's cognitive theory of depression (Beck, 1967,1987; Beck, Rush, Shaw, & Emery, 1979), negative self-schemata involving themes of inadequacy, failure, loss, and worthlessness are hypothesized to contribute vulnerability to depression. These negative self-schemata are often represented as a set of dysfunctional attitudes, such as "If I fail partly, it is as bad as being a complete failure" or "I am nothing if a person I love doesn't love me." When people with such dysfunctional attitudes encounter negative life events, they are hypothesized to develop negatively biased perceptions of their self (low self-esteem), world, and future (hopelessness), which then lead to depressive symptoms. Although hopelessness theory and Beck's theory differ in terms of some of their specifics, both hypothesize that cognitive vulnerability operates to increase risk for depression through its effects on processing or appraisals of personally relevant life experiences. Despite this similarity, however, studies have suggested that the negative attributional style component of cognitive vulnerability as defined by the hopelessness theory and the dysfunctional attitude component of Beck's theory do represent distinct constructs (e.g., Gotlib, Lewin-sohn, Seeley, Rohde, & Redner, 1993; Haeffel et al., 2003; Joiner & Rudd, 1996; Spangler, Simons, Monroe, & Thase, 1997).
A powerful strategy for testing these cognitive vulnerability hypotheses is the behavioral high risk design (e.g., Alloy, Lipman, & Abramson, 1992;
Depue et al., 1981). Similar to the genetic high risk design, the behavioral high risk design involves studying individuals hypothesized to be at high or low risk for developing a particular disorder, but who do not currently have one. In a behavioral high risk design, however, individuals are selected based on hypothesized psychological, rather than genetic, vulnerability or invulnerability to the disorder. For example, in testing the cognitive theories of depression, researchers would want to select nondepressed individuals who either have or do not have the hypothesized depresso-genic cognitive styles. These groups of cognitively high and low risk individuals can then be compared with respect to their likelihood of having had past occurrences of depression (retrospective design) and their likelihood of experiencing depression in the future (prospective design).
Studies using or approximating a behavioral high risk design have provided substantial support for the cognitive theories of depression. For example, Alloy et al. (1992) utilized a retrospective behavioral high risk design to test the attributional vulnerability hypothesis of the hopelessness theory. They examined the occurrence of major depressive disorder (MD) and HD during the previous 2 years in currently nondepressed undergraduates who either did or did not exhibit attributional vulnerability for depression (indicated by an internal, stable, and global attributional style for negative events). Consistent with the hopelessness theory, they found that attributionally vulnerable students were more likely to exhibit past MD and HD, experienced more episodes, and experienced more severe episodes of these disorders than attributionally invulnerable students. In addition, several other studies approximating a prospective behavioral high risk design have reported that people with negative cognitive styles are more likely to develop depressive moods or symptoms when they experience negative life events than are individuals without such negative styles (e.g., Alloy & Clements, 1998; Alloy, Just, & Panzarella, 1997; Metalsky, Halberstadt, & Abramson, 1987; Metalsky & Joiner, 1992; Metalsky, Joiner, Hardin, & Abramson, 1993; Nolen-Hoeksema, Girgus, & Seligman, 1986, 1992).
These positive results stand in contrast to those found when utilizing typical "remitted depression" designs, which generally have found little support for the cognitive vulnerability hypotheses (e.g., Barnett & Gotlib, 1988; Persons & Miranda, 1992; Segal & Ingram, 1994). In these studies, the cognitive styles of individuals who have recovered from depressive episodes are compared to the cognitive styles of individuals with no history of depression. However, there are several problems with using a remitted depression design to test cognitive vulnerability hypotheses (see Alloy, Abramson, & Just, 1995; Just, Abramson, & Alloy, 2001). For example, depressed individuals are a heterogeneous group and the cognitive theories of depression seek to account for only a subgroup of depressives
(i.e., only those with a cognitively mediated subtype of depression). Given that only a subset of such previously depressed individuals are likely to have had a cognitively mediated depression, such heterogeneity can result in equivocal findings when comparing a group of remitted depressed individuals to nondepressed individuals, some of whom may also have a cognitive vulnerability, but have not yet had a depressive episode.
Therefore, in keeping with the suggested methodology already presented, the Temple-Wisconsin Cognitive Vulnerability to Depression (CVD) Project uses a prospective behavioral high risk design to test the cognitive vulnerability and other etiological hypotheses of the hopelessness theory and Beck's theory of depression. The CVD project is a collaborative, two-site study that assesses, among other factors, individual's cognitive styles, the occurrence of negative life events, and the occurrence of both depressive symptoms and clinically significant depressive episodes. This chapter reviews the major findings to date from the CVD project.
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