morbidity and mortality. Expected outcomes include increased confidence and a sense of control in relation to self, improved coping with one’s illness, and more effective interactions with others, particularly medical professionals. Together, these outcomes promote a helpful sense of self-efficacy in dealing with the varied challenges of the illness and its treatment (Bandura, 1997; Thaxton et al., 2005; Ussher et al., 2006).

Peer support groups are widely used to help people with a broad range of illnesses. One of the largest and most successful is Alcoholics Anonymous. Support groups for people living with HIV or AIDS are another example (Spirig, 1998). Such groups are often developed by individuals who feel marginalized socially by their illness because of the associated stigma, disfigured appearance, embarrassment, disability, or threat to life (Davison et al., 2000). After World War II, assisted by the American Cancer Society, patients who had had a laryngectomy, colostomy, or mastectomy began to form support groups in major cities to help cope with these permanent and stigmatizing body changes. Today, support groups for cancer patients are organized through nonprofit advocacy organizations—some devoted to patients with a particular form of cancer (e.g., The Leukemia & Lymphoma Society) and others, such as Gilda’s Clubs, The Wellness Community, and CancerCare, with a more general focus. These support groups are the most widely available form of free psychological assistance for patients with cancer.

Peer groups have developed to help patients of all ages cope with cancer in all of its stages: at diagnosis, during active treatment, and during advanced disease (Plante et al., 2001). They are used most widely by patients with particular forms of cancer, the most common being prostate and breast (e.g., Us Too groups for prostate cancer and breast cancer support groups) (Goodwin, 2005). Today, the support offered by such groups frequently includes services from a health or human services professional, such as a physician, nurse, psychologist, or social worker, who facilitates group meetings or provides patient education or other services to the group. In fact, many groups that are called peer groups actually have co-leaders who are professionals. This involvement from health care providers often makes a “pure” peer group difficult to define; most groups today are to some extent hybrids involving both consumer peers and professionals. Research comparing peer and professionally led support groups has found no difference as long as the sense of community and mutual respect is maintained (Barlow et al., 2000).

Research on the effectiveness of peer support groups has been difficult because such groups often arise naturally out of communities when people sense a need,³ and therefore do not easily lend themselves to the control of variables as is required to conduct controlled clinical trials. The varied