For some time now, scientists have wondered whether some link exists between depression and diabetes, but any research into the matter has proved inconclusive due to limitations of the observational method. Today, a new study published in Diabetologia connects the dots between diabetes and depression while also tying in other key mental health conditions: impulse control disorders, including bulimia and binge eating disorder. “So now we know that depression and impulse control disorders are probably the most important mental health problems associated with diabetes,” Dr. Peter de Jonge, professor in the Interdisciplinary Center for Psychopathology and Emotion Regulation at the University of Groningen, Netherlands, told Medical Daily in an email.

The possible connection between depression and diabetes has intrigued scientists for good reason. If researchers could prove the presence of depression increases the risk of future diabetes, then treatment and alleviation of depression might very well translate into a decreased risk of diabetes. Consider, too, that the typical age when depression begins (25 years old) is substantially younger than the typical age when type 2 diabetes begins (45 years or older). This means, then, there would be significant lead time to cure depression and in so doing, reverse a possible diabetes diagnosis. Yet de Jonge, who understood the potential relationship between depression and diabetes, suspected there might be other more important factors in play. “Mental health conditions are often associated, that is, if a person has condition A, this person will have an increased risk of having condition B as well,” de Jonge told Medical Daily.

“There has been a lot of research that suggests that depression relates to diabetes. But it remains possible that this association is really due to an 'underlying third factor' that is associated with both depression and diabetes. For instance it is possible for a person to first develop an eating disorder, then to develop depression and then diabetes. If you would look only at depression and diabetes you would conclude that it is due to depression. But once you look at the whole spectrum of mental health problems you get a more complete picture.”

Global Study

To examine diabetes as it relates to a spectrum of mental health disorders, de Jonge worked with colleagues around the globe. The team of researchers collected data on diabetes and a range of preexisting mental disorders and performed a series of face-to-face surveys of adults in 19 countries: Colombia, Mexico, Peru, USA, Shenzhen (China), Japan, New Zealand, Belgium, France, Germany, Italy, the Netherlands, Romania, Spain, Portugal, Israel, Iraq, Northern Ireland, and Poland. Next, the researchers examined and compared the collected data.

In particular, the researchers focused on 16 mental disorders: anxiety disorders (including PTSD, obsessive–compulsive disorder, panic disorder, and social phobia); mood disorders (including depression and bipolar disorder); impulse control disorders (bulimia, intermittent explosive disorder, and binge eating disorder), and substance use disorders. Depression and dysthymia, a less severe but longer-lasting strain of depression, were analyzed together, while anorexia nervosa was excluded because not enough sufferers existed to establish reliable data. Overall, the researchers identified 2,580 cases of adult-onset diabetes mellitus. After making the necessary statistical adjustments, only depression, intermittent explosive disorder, binge eating disorder, and bulimia nervosa were associated with a diabetes diagnosis. In fact, the researchers found about a 30 percent increased risk of diabetes in cases of depression, after they weeded out those who had a second mental health diagnosis. “These findings … suggest that the association between depression and diabetes is relatively independent from other psychiatric disorders,” wrote the authors in their published research.

Although the above result was somewhat expected, the researchers were surprised to find a 60 percent increased risk of diabetes in cases of intermittent explosive disorder.  Similarly, binge eating disorder and bulimia nervosa also pushed the needle toward an increased risk of diabetes by 2.6 times and 2.1 times, respectively. “The association between impulse disorders and diabetes diagnosis has not been reported before,” the authors concluded in their paper. “By far the strongest prospective associations were found with respect to eating disorders and diabetes.” What's more, the team's work with diabetes continues, according to de Jonge, who told Medical Daily, “We are doing a new study in the Netherlands, Lifelines, in which we will follow people for many years so that we can see if mental health problems that occur early in life really predict the onset of diabetes (and other somatic illnesses).”

And in the meantime? “It remains possible for a person to develop an eating disorder, become depressed later on, and in the end develop diabetes mellitus,” the authors noted, “Targeting the eating disorder in this case will theoretically be a far more promising approach than focusing solely on depression.”

 

Source: de Jonge P, Alonso J, Stein DJ, Kiejna A, Aguilar-Gaxiola S, Viana MC, et al. Associations between DSM-IV mental disorders and diabetes mellitus: a role for impulse control disorders and depression. Diabetalogia. 2014.