The role of psychological factors in cancer onset and progression.

Psychological factors have been presumed to play a role in cancer initiation and progression. This article critically reviews the literature on cancer and its potential connections to affective states, coping/defensive styles and personality traits, behaviors, and stressful life events. Much of the existing research is flawed by poor study design and analysis that have limited the reliability and validity of both negative and positive studies. While some psychological factors can be associated with cancer onset and progression, no direct links have been established. Recent studies have documented some medical and psychosocial benefits of psychotherapeutic intervention in patients with cancer.