Cancer and Depression
Depression and cancer interact in many ways: cancer patients have higher rates of depression and depression can in turn increase cancer risk, complicate the course of cancer and its treatment and even speed progression. Indeed, patients with medical illness are at elevated risk for depression (Katon & Sullivan, 1990).
Depression also complicates patients' efforts to cope with the illness and adhere to medical treatment. While many cancer patients do not suffer with depression, a substantial minority do.
Yet this comorbid psychiatric illness is frequently overlooked, since its symptoms are easily misattributed to cancer and its treatment. Pervasive sadness and hopelessness can be "explained" as a reaction to poor prognosis, sleep disturbance to disease-related anxiety and poor appetite to chemotherapy side effects.
Thus, depression can be a complicating problem for a substantial minority of people with chronic medical illnesses, including cancer (Spiegel, 1996). The relationship between cancer and depression is bi-directional. More rapid progression and increased symptoms of cancer are associated with more severe depression, (Bukberg et al., 1984), while comorbid depression is associated with increased functional impairment and poorer quality of life over the course of chronic illness (Katon & Sullivan, 1990;Weitzner et al., 1997).
As cancer treatment improves, the disease is being converted from a terminal to a chronic illness. Half of all people diagnosed with cancer will live to die of something else, so more people are living to cope with the disease, its treatment, the threat of recurrence and complicating psychiatric disorders.
A number of studies have documented a substantial prevalence of depression and depressive symptoms among cancer patients. Not surprisingly, the more narrowly the term "depression" is defined, the lower the prevalence of depression reported. Reported rates of depressive symptoms vary from 25% to 50% in samples of hospitalized cancer patients (Derogatis et al., 1983; Massie & Holland, 1990; Hopwood et al., 1991; McDaniel et al., 1995; Pasacreta, 1997).
Factors associated with greater prevalence of depression are pain, a higher level of physical disability and more severe illness. Even in studies that make quite conservative estimates of depressive symptoms (Lansky et al., 1985) the rates of major depression (5.3%) are comparable or slightly higher than the 3-5% six month prevalence found in the general population (Blazer et al., 1994).
Derogatis et al (1983) examined the prevalence of psychiatric disorders in 215 oncology inpatients randomly selected from three cancer centers (excluding those gravely physically disabled) and found that 47% had clinically apparent psychiatric disorders (6% major affective disorders; 12% adjustment disorders with depressed mood and 13% adjustment disorders with mixed emotional features).
Nearly 90% of the psychiatric disorders observed were judged to be reactions to or manifestations of disease or treatment. Intrusive thoughts and memories of stressful life events, mostly cancer-related, complicate and intensify subsequent anxiety and depressive symptoms in cancer patients (Brewin et al., 1998).
Up to 32% of women with breast cancer report elevated levels of depressive symptoms (Fallowfield et al.,1990; Hopwood et al., 1991; McDaniel et al., 1995; Pasacreta, 1997). Aragona and colleagues (1997) found that 13% of a sample of women diagnosed but not yet treated for breast cancer met diagnostic criteria for dysthymic disorder, compared with 5% of controls. 62 % of these newly diagnosed patients had some depressive symptoms, although only 2% met full criteria for major depression.
The finding that a substantial minority of cancer patients suffer from major depression and dysthymia has been supported across cultures as well, rates being similar in Japan (28% of a group of mixed cancer patients) (Hosaka & Aoki, 1996) and Australia (minor depression in 27.1% of primary breast cancer patients and major depression in 9.6% (Kissane et al., 1998).
One encouraging finding from a meta-analysis of 58 studies is that the prevalence of depression among cancer patients seems to be lower during the past two decades than it was previously (van't Spijker et al., 1997). This may reflect improvements in treatment, including less mutilating surgical interventions (e.g. lumpectomy vs. mastectomy for breast cancer (Levy et al., 1992; Pozo et al., 1992; Wellisch & Carr, 1991), improved medical outcomes (Peto et al., 2000) and an improved atmosphere of social support for cancer patients (Spiegel, 2001).
Rates of depressive states reported for cancer inpatients are roughly comparable to those reported for similarly ill patients with other medical diagnoses (Evans et al., 1999). Studies of medical inpatients show that about one-third report mild or moderate symptoms of depression and up to one-fourth may suffer from a depressive syndrome (Katon & Sullivan, 1990; Atkinson et al., 1988).
Poorer quality of life
Comorbid depression, in turn, is associated with increased functional impairment and poorer quality of life over the course of chronic illness (Katon & Sullivan, 1990; Weitzner et al., 1997). These studies suggest that the severity of the medical illness, irrespective of its underlying cause, is the factor most closely associated with the frequency of both depressive symptoms and syndromes. Indeed the prevalence of major depression is as much as two-thirds of terminally ill patients requesting assisted suicide (Chochinov et al., 1995).
However, depression in patients with cancer has been underdiagnosed and undertreated due in part to the belief that depression is a normal and universal reaction to serious disease (Rodin & Voshart, 1986; Spiegel, 1996); and in part because the neurovegetative signs (weight loss, sleep disturbance) or emotional/cognitive signs of depression are often attributed to the medical illness itself. (McDaniel et al., 1995; Craig et al., 1974).
Depression and cancer pain
More rapid progression and increased symptoms of cancer, especially pain (Spiegel & Bloom, 1983b), are associated with more severe depression, (Bukberg et al., 1984; Spiegel et al., 1994) while comorbid depression is associated with increased functional impairment and poorer quality of life over the course of chronic illness (