months preceding the onset of their depression, 50–80 percent of depressed persons had experienced a major life event, compared with only 20–30 percent of nondepressed persons evaluated during the same time period (Monroe and Simons, 1991). Approximately 20–25 percent of people who experience major stressful events develop depression (van Praag et al., 2004). Moreover, there is consistent evidence that severe events are more strongly associated with the onset of depression than are nonsevere events, and that there may be a dose-response relationship between the severity of major life events and the likelihood of depression onset (Monroe and Simons, 1991; Kessler, 1997). In general, major life events that are undesirable and uncontrollable, such as bereavement or job loss, are the most likely to be associated with depression (Mazure, 1998). Life-threatening illnesses have also been associated with an increased risk of depression (Dew, 1998). The greatest prevalence of depression in chronically ill patients is reported among those with greater pain, higher levels of physical disability, and more severe illness (Krishnan et al., 2002).
Prospective research conducted among initially healthy populations provides considerable support for a link between stress and incident cardiovascular disease (CVD) (Rozanski et al., 1999; Krantz and McCeney, 2002; Belkic et al., 2004). Research examining the influence of chronic psychosocial stress on the risk of recurrent events among persons with preexisting CVD is not as extensive. However, findings from this literature further suggest that exposure to chronic or ongoing psychosocial stress may play a role in worsening disease prognosis among persons with a known history of CVD. Perceived life stress (Ruberman et al., 1984), excessive demands at work (Hoffmann et al., 1995), marital distress (Orth-Gomer et al., 2000; Coyne et al., 2001), and social isolation (Mookadam and Arthur, 2004) each have been related to poor CVD outcomes (i.e., recurrent events and/or mortality) among persons with preexisting CVD. In addition, short-term stressful events and episodes of anger have been shown to precipitate clinical manifestations of coronary artery disease such as myocardial infarction (Rozanski et al., 1999; Krantz and McCeney, 2002). Reviews of prospective studies generally conclude that depression is an important risk factor both for onset of CVD among initially healthy persons (Rugulies, 2002; Wulsin and Singal, 2003; Frasure-Smith and Lesperance, 2005) and for worsening prognosis among CVD patients (Barth et al., 2004; van Melle et al., 2004; Bush et al., 2005). Several studies have also shown that social support is associated with lower resting and ambulatory blood pressures (Uchino et al., 1999; Ong and Allaire, 2005)—a factor reducing the risk of