New study links diabetes, depression, and death

October 24, 2005

A recent study examining the relationship between diabetes, depression, and death demonstrates a need for diabetes patients and pharmacists to be familiar with the symptoms of depression. "We know that people with diabetes who have depression are at a much greater risk of mortality than similar people without diabetes," said Xuanping Zhang, Ph.D., a researcher with the National Center for Chronic Disease Prevention and Health Promotion at the Centers for Disease Control & Prevention in Atlanta. "Pharmacists and physicians have a professional obligation to let patients suffering from diabetes and depression know of this risk. Absence of intervention can be life-threatening."

An awareness of studies linking depression and diabetes enhances the ability of pharmacists to properly do their job, said Zhang. For example, they can inform diabetes patients of a possible need to address the issue of depression with their primary care physicians. Therefore, R.Ph. awareness of the symptomology of depression is imperative.

"Treatment of depression has become a responsibility of providers in all healthcare settings," agreed Glen L. Stimmel, Pharm.D., professor of clinical pharmacy and psychiatry at the University of Southern California Schools of Pharmacy and Medicine. "And successful treatment of depression requires both precision in diagnosis and careful monitoring and fine-tuning of pharmacotherapy over time," he added.

Recognition of depressive symptoms among diabetes patients can be a matter of life and death, said Zhang. He led a group of CDC and Agency for Healthcare Research and Quality researchers in an analysis of data from the National Health and Nutrition Examination Survey (NHANES). First, they identified 558 people with diabetes and 7,063 without the disease. Depressive symptoms of each group were determined with a questionnaire. Their findings are alarming.

The researchers found that people with diabetes who struggle with depression have a significantly greater risk of mortality than others. Those with the highest depression scores had a 54% greater mortality rate within a 10-year follow-up period than did people with the lowest scores. The results held true after participants were matched for socioeconomic factors, lifestyle, and health-status variables, said Zhang. At the same time, no apparent relationship was noted between depression and mortality among the nondiabetic population.

"Our work shows that the relationship between depression and mortality is different in people with and people without diabetes," said Zhang. "Depression should be considered a target for diabetes management interventions. The study also points to the need to study subgroups, such as diabetes patients, rather than aggregated populations, when examining the effect of depression on mortality."

The results of the study were published in the April 1 issue of the American Journal of Epidemiology in an article titled "Depressive Symptoms and Mortality among Persons with and without Diabetes." Although Zhang's work does not determine a causal relationship between depression and diabetes, the study does support a body of research that ties the two diseases. "Depressed persons may be more likely to adopt unhealthy behaviors, such as a sedentary lifestyle and a poor diet, which are in turn associated with a greater likelihood of obesity and Type 2 diabetes," he said. "But the causes of the relationship between death, depression, and diabetes remain unclear."

Whatever the cause, it is certain that people with diabetes are at greater risk for depression than the general population, according to the National Institute of Mental Health. In addition, individuals with depression may be at greater risk for developing diabetes, according to an NIMH position paper titled "Depression and Diabetes." NIMH's research demonstrates that the risk of depression could be doubled in diabetes patients compared with those without the disorder and the chances of becoming depressed increase as diabetes complications worsen.