impair the ability to learn and maintain new behaviors (Spiegel, 1997) or to undertake complex tasks that require planning and behavioral execution (Wells and Burnam, 1991; Olfson et al., 1997).
For example, research on kidney transplant recipients’ adherence to immunosuppressive medication has found that patients with poor adherence report higher levels of psychological distress relative to patients with good adherence (Achille et al., 2006). Patients undergoing dialysis treatment for end-stage renal disease have also been found to experience greater cognitive impairment and dysfunction due to depressive mood (Tyrrell et al., 2005). Disturbance of mood and motivation in HIV-positive individuals has been associated with decrements in several cognitive factors, such as neurocognitive performance, verbal memory, executive functioning, and motor speed (Castellon et al., 2006). Among patients with advanced cancer, depression and anxiety similarly have been found to contribute to cognitive impairments (Mystakidou et al., 2005). Even after controlling for the effects of pain and illness severity, anxiety and depression among patients with cancer have been independently associated with decreased cognitive functioning (Smith et al., 2003).
Moreover, when patients are distraught about the course of their illness, they may be more likely to forget health professionals’ recommendations and less likely to ask questions about their care and participate in medical visits (Robinson and Roter, 1999; DiMatteo et al., 2000; Katon et al., 2004; Sherbourne et al., 2004). Lower levels of patient participation are associated with poorer health behaviors (Martin et al., 2001).
Distressed psychological states can limit patients’ concern about the importance of their health behaviors and contribute to their belief that the benefits of adherence are not worth the trouble (Fink et al., 2004). Distressed psychological states can also lead to diminished self-perceptions and limitations in personal self-efficacy,5 which in turn negatively affect health behaviors and adherence. Pessimism about the future and about oneself can forestall the adoption of new health practices and interfere with health behaviors and adherence (Peterman and Cella, 1998; DiMatteo et al., 2000; Taylor et al., 2004). Limitations in personal self-efficacy that derive from both anxiety and depression can interfere with the behavioral commitment essential to the adoption and maintenance of new health practices. Distressed psychological states can also amplify somatic symptoms, causing