of parental lack of care, plus exposure to high levels of chronic and episodic stressors. Such environments contribute to dysfunctional cognitions and coping skills that increase vulnerability to depression. Neurobiological mechanisms may also be implicated, with the speculation that severe stress early in life alters the brain’s neuroregulatory processes, which promote susceptibility to depression (e.g., Heim and Nemeroff, 2001). Exposure to adverse conditions in childhood may sensitize the youth to stress, so that it may take minimal exposure to later stressful life events to precipitate depression in them compared with those without childhood adversity (e.g., Hammen, Henry, and Daley, 2000; Harkness, Bruce, and Lumley, 2006).

As noted earlier, etiological approaches to depression commonly invoke diathesis-stress models, in which stress precipitates depressive reactions among those with particular vulnerabilities. In this section, several nonbiological vulnerabilities are discussed: cognitive, interpersonal, and personality factors. As with biological factors, psychosocial vulnerabilities may contribute to the development of depression and also may be consequences of depressive states in a bidirectional process.

Considerable research on depression in the past 40 years has focused on three variants of cognitive models of depression—the classical cognitive triad model (negative views of the self, world, and future) of Aaron Beck (e.g., 1967, 1976), the versions of the helplessness/hopelessness cognitive style models of Seligman, Abramson, Alloy, and colleagues (e.g., Abramson, Metalsky, and Alloy, 1989; Abramson, Seligman, and Teasdale, 1978), and information-processing perspectives (e.g., reviewed in Joorman, 2008).

The Beck and cognitive style models emphasize the role of distortion in the content of thinking of depressed people. Those at risk for depression are hypothesized to have characteristic ways of interpreting events and circumstances that are excessively pessimistic and self-critical, with perceptions of helplessness and hopelessness about changing or improving their situations. Such underlying beliefs may be activated in the face of undesirable events, so that life events—even minor or fairly neutral experiences—are seen as reflections on one’s underlying lack of worth and competence. Such views lead to the exacerbation and maintenance of symptoms of dysphoria and futility, sometimes to the extent of major depressive episodes and suicidality. Ample evidence has accumulated that verifies that, when experiencing depressed moods or episodes, a person’s thinking is considerably more negative than he or she would display when not in a depressed mood (e.g.,