A growing body of evidence clearly supports the link between diabetes and depression. A meta-analysis of 39 studies of patients with diabetes reported an estimate of major depression in 11% of the patients and elevated depressive symptoms in 31%.1
People with diabetes have double the odds of having depression, compared with the general population.2 Predictors of depression in patients with diabetes include female sex, younger age, less education, lower income, smoking, obesity, and multiple diabetic complications.1
It is important to recognize the link between diabetes and depression for several reasons3,4:
In addition to these problems with clinical outcomes, patients with depression may lack support from family or friends, have a negative view of themselves, view barriers to medication use as overwhelming, or perceive that the desired outcomes of treatment will not occur. These problems greatly affect patients'ability to care for themselves and achieve the desired outcomes of therapy.
It is not clear the extent to which these diseases affect each other. Depression is believed to decrease physical health by a combination of biological and psychological changes.5 Psychological stress is thought to increase susceptibility to disease; persistent somatic symptoms of depression are thought to worsen physical health over time; and depressed mood may decrease the likelihood that patients will seek treatment and adhere to prescribed self-care and medication treatment regimens. Diabetes, on the other hand, affects functional ability because of the development of complications, such as vision difficulties, neuropathy, peripheral vascular disease, and lower-extremity ulcers.
Treatment of depression improves outcomes in patients with diabetes. Several studies have demonstrated that patients with diabetes who received medication or cognitive behavioral therapy had improved depression scores and improved glycemic control, compared with patients who received either a placebo or diabetes education alone.6,7 In addition, treated patients achieved medication adherence scores that were equal to those of patients without depression.
Several approaches may be used to help depressed diabetic patients. Case management services, which may include screening for depression, may help improve depression scores, perhaps through increased referrals to appropriate care, but they have not been demonstrated to improve glycemic control.
Clinical pharmacists, in collaborative care models, also have been used to improve care in these patient populations, although specific studies evaluating pharmacist care in depressed diabetics have not been done. A Kaiser Permanente model used clinical pharmacists to manage medication therapy for depression after the initial diagnosis had been established by a physician. Pharmacists documented target symptoms, identified stressors for the patient, and recommended treatment. Within this system, they were able to modify dosing regimens and recommend alternative therapies if treatment failed.8
Pharmacist-managed diabetes clinics have been shown to improve glycemic control and adherence to the American Diabetes Association guidelines for therapy. In addition to improvement in hemoglobin A1C measurements, referrals were made more frequently for dietary instruction, podiatric care, and evaluation of diabetic retinopathy, compared with physician-managed patients.9,10
The link between diabetes and depression is very complicated. Health care costs for untreated patients may be enormous. Treatment with appropriate medications may significantly improve both psychological and physical outcomes. Pharmacists have the opportunity to play a significant role in the identification and management of patients afflicted with either or both of these diseases.
Dr. Garrett is a clinical pharmacist practitioner at Cornerstone Health Care in High Point, NC.
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