Depression is associated with inflammatory and autoimmune diseases in many situations. Studies of diabetic patients have reported a wide range of results, from 3.8 to 27.3 percent also experiencing depression.
Researchers at The University of Colorado pointed out that many investigations have not distinguished between type 1 and type 2 diabetes in relation to depression. While both types of diabetes have similar symptoms and require similar lifestyle adjustments, type 1 may be expected to have a significantly greater association with depression. Type 2 is caused by insulin resistance, and is not currently believed to involve inflammation or immune damage. Type 1, on the other hand, is caused by autoimmune damage to the pancreas. The autoimmune process is associated with elevated levels of inflammatory cytokines which are believed to produce depressive symptoms in a variety of conditions.
The Colorado authors reported a remarkable 32.1 percent rate of depression in the type 1 diabetic patients in their study, compared to 16.0 percent in matched control subjects. Their data come from the Coronary Artery Calcification in Type 1 Diabetes (CACTI) Study, in the time frame from 2006 to 2008. The control subjects were recruited from the same community, including spouses, friends, and neighbors of the diabetic patients. This was done to minimize the environmental differences between diabetic patients and non-diabetic controls. The study included 458 diabetic patients and 546 controls. Depression was measured in two ways, by use of anti-depressants and by the the Beck Depression Inventory II (BDI-II) self-report instrument. Scores greater than 14 on the BDI-II and/or current use of anti-depressants was counted as depression.
The authors concluded that their results are higher than previous reports of depression in diabetes for two reasons: 1-other studies included a mixture of type 1 and type 2 diabetes patients, and 2-different studies use different criteria to define depression.
Depression is associated with complications of diabetes, including coronary artery disease. There are several possible explanations for this.