Insulin resistance predicted the development of major depressive disorder in adults over the course of nine years, according to a study published today in AJP in Advance.
“Several studies have shown an association between insulin resistance and depression, including our previous work,” Katie Watson, Ph.D., a postdoctoral scholar in the Department of Psychiatry and Behavioral Health at Stanford School of Medicine, told Psychiatric News. “We did not know whether being insulin resistant first could lead to new cases of depression in the future. Here we see that insulin resistance, a highly prevalent condition that often precedes type 2 diabetes, is also associated with an increased rate of depression.”
At baseline, researchers examined three surrogate measures of participants’ insulin resistance: the ratio of triglycerides to high-density lipoprotein (HDL); prediabetes, as measured by fasting plasma glucose level; and waist circumference. Participants included 601 adults in the Netherlands with no history of depression, anxiety, or other psychiatric disorders. Researchers conducted additional physical and psychiatric interviews and screenings at 2, 4, 6, and 9 years, and results were adjusted for behavioral and sociodemographic variables.
Researchers reported that higher triglyceride-HDL ratio at baseline increased risk for major depression by 89% in the nine-year follow-up. Similarly, higher fasting blood glucose levels increased major depression risk by 37% during the course of the study. A 2-inch increase in waist circumference at baseline corresponded to an 11% increased rate of major depression on average.
In addition, researchers found that the development of prediabetes within two years of study enrollment was associated with a nearly threefold risk of developing major depressive disorder during the seven years of the study. According to the National Institutes of Health, about 1 of 3 adults in the United States is prediabetic, and some antipsychotics increase the risk of prediabetes.
“[The] ability to predict an increased risk in major depressive disorder incidence using standard clinical tests of metabolic status can be deployed as an important tool for treatment and prevention. Indeed, our own work suggests that certain treatments that decrease insulin resistance can aid in the treatment of major depression in a subset of patients,” wrote Kathleen Rasgon, M.D., Ph.D., and colleagues. “It will be especially important to ascertain in future studies whether reversing insulin resistance is able to decrease the risk of future clinical depression.”
For related information, see the Psychiatric News article “Insulin Levels, BMI in Youth May Be Linked to Psychosis, Depression Risk in Adulthood.”
(Image: iStock/towfiqu ahamed)
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