Depression can speed onset of Type 2 diabetes

Risk factor for diabetes as well as other conditions

Researchers have long known of the link between diabetes and depression, although no one is certain which comes first. They’ve also thought the depression meant that patients did not take good care of themselves and therefore had poor glycemic control.

But now a study from Washington University in St. Louis shows that the increases in cortisol relate to depression and that leads to hyperglycemia, for the first time linking the physiological effects of the two disorders. Furthermore, depression — even in patients with pre-diabetes or impaired glucose tolerance — may promote insulin resistance and speed the onset of Type 2 diabetes, says lead author of the paper, Patrick Lustman , PhD. Lustman is a professor of medical psychology and director of the Office for the Study of Stress and Depression in Diabetes at Washington University School of Medicine.

Lustman presented his research at the 59th Scientific Sessions of the American Diabetes Association in San Diego in June. He estimates that 15% to 20% of all Type 2 diabetics suffer from major depressive disorders and perhaps as many as 90% of people with Type 2 diabetes have episodes of depression. "Depression is a risk factor for Type 2 diabetes," he says, noting it may not get as much press as obesity.

Lustman and his colleagues are looking at the physical effects of depression at multiple levels from onset to the progression of the disease and its complications. In three studies, Lustman has found that successfully treating depression results in improved glycemic control — with patients reducing their HbA1c levels by .4 to 1.2%. "Nowhere else in medicine had there been as good a case made for treating an emotional problem and improving a patient’s medical condition," Lustman says.

"Diabetes causes abnormalities in neurotransmitter function," he continues. "Those abnormalities in dopamine and serotonin production have strong implications in depression." He found that cognitive behavioral therapy, a form of psychotherapy designed for the treatment of depression, helped bring 85% of the diabetic patients in his study into remission.

Treatment was effective, but it is rarely permanent, as 80% of all depressed patients have recurrences and afflicted patients are rarely without symptoms for more than a year at a time.

In the cognitive behavioral therapy study, Lustman found that 92% of the patients treated averaged 4.8 episodes of recurrence of depression within a five-year follow-up period. He says further studies will provide more information about the effectiveness of cognitive behavioral therapy and maintenance anti-depressant medication.

In the paper presented at the ADA sessions, Lustman found that depressed diabetics experienced 31% more bodily pain, considered themselves 49% less vital than controls, and had lower scores on self-reported general health, mental health, and physical and social function.

Lustman also found that recurring depression was dependent on the severity of a patient’s medical condition and particularly the presence of neuropathy at the entry point.

"We have found that the status of a patient’s diabetes determines the course of the disease," Lustman says. "It’s not really surprising since diabetes is a major stressor in itself. The disease is a roof that imposes itself over everything in his life. There are worries about complications. It’s hard to feel good when you’ve got an open sore on your foot that won’t heal."

Mark Peyrot, PhD, of the Loyola College Center for Social and Community Research in Baltimore, found that diabetic patients at the highest risk of persistent depression were those who had more than two complications of the disease, were not treated with insulin, and who did not graduate from high school.

Lustman says the vast majority of diabetics with depression are not recognized by their physicians. "Probably two-thirds of the patients with depression are never diagnosed or treated," Lustman says. "Doctors need to ask patients about their state of mind and quality of life."

Even though doctors are pressed for time, Lustman says, they would likely find significant improvements in their patients’ glycemic control if depression is treated pharmacologically and/or with psychotherapy. "If doctors would just rely on a couple of quick questions, we’d have much better results."

Unfortunately, in many primary care practices, patients who are diagnosed with depression are simply given anti-depressant medications without any emotional support or follow-up until the next semi-annual visit. A patient has a 25% chance of improving mentally and physically with treatment for depression, and that 25% is "no small prize in terms of quality of life," Lustman asserts.

He suggests asking patients these questions if they seem to be at risk of depression:

1. Have you been feeling sad for more than two weeks?

2. Has your activity level changed?

Even more effective, Lustman says, is the Beck Depression Inventory, a brief paper-and-pencil test in which the patient answers 21 questions. It measures cognitive and somatic symptoms that he says would point out about 70% of depressed diabetic patients.

Lustman’s findings are similar to Peyrot’s latest paper on Type 1 disease, published in the June issue of the Journal of Health and Social Behavior. In this study, Peyrot found that stress-related lapses in self-care resulted in poor glycemic control among the patients who can least afford it physiologically. Patients with Type 1 diabetes are more vulnerable than those with Type 2 to stress-related lapses in blood sugar maintenance, and failure to attend to these matters can have disastrous consequences.

In an earlier study, Peyrot found that 41.3% of all adult diabetics suffered from depression and 49.2% from anxiety, far higher than in the general population where estimated rates of depression and anxiety range between 10% and 20%.

Researchers at Kaiser-Permanente’s Center for Health Research in Portland, OR, found the cost of treating depressed diabetic patients was 68% higher than all cost expenditures on nondepressed nondiabetic patients.

Gregory A. Nichols , PhD, a senior research assistant at Kaiser, says his organization has a data base of 35,000 diabetic patients treated since 1988, so there are ample opportunities to study issues like the links between depression and diabetes.

"We found people who are depressed are more likely to be taking insulin," Nichols says. "Also, the depressed group tended to be younger, were more likely to be female, had more comorbidities, and have a higher BMI [body mass index]."

[For more information, contact Patrick Lustman at (314) 362-2441 and Gregory Nichols at (503) 335-6733.]