What Is the Link Between Depression and Diabetes?

Many of the more than 15 million Americans who suffer from depression each year might be surprised to learn that they are now at risk for developing Type 2 diabetes. This is not a new finding: it is the sort of fact that a physician assumes everyone knows. In fact, the association between the two diseases was first mentioned in 1684, when the English physician Thomas Willis noted that emotional factors (such as grief or sadness) could bring on diabetes. Of course most patients don’t know this, and should they be among the 10% of U.S adults who develop diabetes ( 23% of adults over 60), it probably would never occur to them that depression might be behind developing this metabolic disease.

Several long term studies have proven rather conclusively the link between depression and diabetes. In a compelling ten-year study, Dr. An Pan and a large research team gathered data on 65,381 adult women aged 50-75 to see what the relationship between diabetes and depression might be. They published their results in The Archives of Internal Medicine about five years ago. ("Bidirectional Association Between Depression and Type 2 Diabetes Mellitus in Women" A Pan, M Lucas, Q Sun, et al Arch Intern Med. 2010;170(21):1884-1891.) The women who suffered from depression had a 17% higher risk of developing diabetes, and this was not related to their weight status or physical activity. If they were on antidepressant medications, they had a 25% higher risk of developing diabetes, compared to women who were not depressed.

And the risk factor may be even greater than this. A few years earlier, an analysis of several studies indicated that adults with depression had a 37% higher risk of becoming diabetic (“Depression as a Risk Factor for the Onset of Type 2 Diabetes Mellitus: A Meta-Analysis,” M. Knol, J. Twisk, A. Beekman, et al. Diabetologia, 2006; 49:837-845).

What could the connection possibly be? No one really knows. The obvious reasons: obesity, poor eating habits, lack of physical activity, weight gain, etc. did not seem to be involved in Dr. Pan’s study of depressed women, although other studies suggest that all of these factors may be involved. Weight gain as a side effect of antidepressive medication is a risk factor for diabetes, and as is the absence of physical activity associated with the fatigue of depression.

Diabetics, especially those who require insulin, have a significantly greater chance of developing depression, so the relationship works both ways. Being diagnosed with this chronic disease has a permanent impact on altering lifestyle, and its potential for developing potentially life threatening side effects certainly increases stress, anxiety, and depression. Diabetics must contend with the effects on their physical and mental well-being of uncontrolled shifts in their blood sugar that may lead to coma, and even death. Even patients experienced with controlling their food intake and insulin requirements to keep their blood sugar constant may be thrown off by an infection, disruptions in sleep, increases in physical activity, and even being premenstrual. And in another example of an ‘unfair’ world, people suffering from both depression and diabetes seem to have a larger number of diabetic symptoms, than diabetics who are not depressed .(Depression and Diabetes Symptom Burden, Ludman, Katon, Russo, et al General Hospital Psychiatry, 2004; 26: 430-436).

Might obesity be one of the links between depression and diabetes? In another mega study, this time with over 55,000 people, researchers from the Netherlands ( Luppino, deWit, Bouvy, et al. Overweight, Obesity and Depression: A Systematic Review and Meta-Analysis of Longitudinal Studies. Arch Gern. Psychiatry 2010; 67: 220-229.) found that obese people have a 55% increased risk of developing depression, and those with depression have a 58% increased risk of becoming overweight over time; both these conditions are associated with diabetes.

Psychiatrists must be even more attentive to the weight gaining risks of antidepressive medication, and diabetes specialists must be sensitive to early signs of depression among their diabetic patients. People whose obesity seems impervious to traditional means of weight loss, i.e. dieting and exercise, should be evaluated to see if bariatric surgery might be the solution. One of the now well established benefits of weight loss after such surgery, is the disappearance of diabetes after only trivial amounts of weight have been lost. Fortunately, depression also decreases significantly after bariatric surgery (“Anxiety and Depression in Bariatric Surgery Patients: a Prospective, Follow-up Study Using Structured Clinical Interviews,” de Zwaan, Enderle, Wagner, Mühlhans, Journal of Affective Disorders (Impact Factor: 3.71). 04/2011; 133(1-2):61-8.). And since we now know that depression may lead to obesity, which may lead to diabetes, which may lead to depression…perhaps decreasing obesity will break this chain, or at least weaken it.