Women suffering from both diabetes and depression have a greater risk of dying, especially from heart disease, a study suggests.
In fact, women with both conditions have a twofold increased risk of death, researchers say.
"People with both conditions are at very high risk of death," said lead researcher Frank B. Hu, MD, PhD, a professor of medicine at Harvard Medical School. "Those are double whammies."
In the United States, some 15 million people suffer from depression and 235 million have diabetes, the researchers say. Up to one-fourth of people with diabetes also experience depression, which is nearly twice as common as among people who don't have diabetes, they added.
Dr. Hu's team collected data on 78,282 women who were aged 54 to 79 in 2000 and who were participants in the Nurses' Health Study.
Over six years of follow-up, 4,654 women died, including 979 who died of cardiovascular disease, the investigators found.
Women who had diabetes had about a 35% increased risk of dying, and those with depression had about a 44% increased risk, compared with women with neither condition, the researchers calculated.
Those with both conditions had about twice the risk of dying, the study authors found.
When Dr. Hu's team looked only at deaths from heart disease, they found that women with diabetes had a 67% increased risk of dying and those with depression had a 37% increased risk of death. But women who had both diabetes and depression had a 2.7-fold increased risk of dying from heart disease, the researchers noted.
When people are afflicted by both diseases, these conditions can lead to a "vicious cycle," Dr. Hu said. "People with diabetes are more likely to be depressed, because they are under long-term psychosocial stress, which is associated with diabetes complications."
People with diabetes who are depressed are less likely to take care of themselves and effectively manage their diabetes, he added. "That can lead to complications, which increase the risk of mortality.
Dr. Hu stressed that it is important to manage both the diabetes and the depression to lower the mortality risk. "It is possible that these two conditions not only influence each other biologically, but also behaviorally," he said.
Type 2 diabetes and depression are often related to unhealthy lifestyles, including smoking, poor diet and lack of exercise, according to the researchers. In addition, depression may trigger changes in the nervous system that adversely affect the heart, they said.
The report was published in the journal Archives of General Psychiatry.
Commenting on the study, Luigi Meneghini, MD, an associate professor of clinical medicine and director of the Eleanor and Joseph Kosow Diabetes Treatment Center at the Diabetes Research Institute of the University of Miami Miller School of Medicine, said the findings were not surprising.
"The study highlights that there is a clear increase in risk to your health and to your life when you have a combination of diabetes and depression," he said.
Dr. Meneghini noted there are many diabetic patients with undiagnosed depression. Patients and doctors need to be more aware that depression is an issue, he stressed. Patients need to tell their doctors if they are feeling depressed, and doctors also need to be on the lookout for signs of depression in their diabetic patients.