Prediabetes, central adiposity and high triglyceride (TG) to high-density lipoprotein (HDL) cholesterol ratio are predictive of developing a major depressive disorder, according to a recent study published in the American Journal of Psychiatry.

The researchers utilized the Netherlands Study of Depression and Anxiety (NESDA) data and recruited 601 participants, aged 18 to 65 years, for their study. None of the study subjects had any history of  depression or anxiety disorders at the time of entry into the study. NESDA is a multisite longitudinal study of the course and consequences of depressive and anxiety disorders in adults. Incident major depressive disorder was selected as the outcome measure. Psychiatric evaluation was conducted at 2, 4, 6, and 9 years and participants were screened for major depressive disorder, anxiety disorders and bipolar disorder. Triglycerides, HDL cholesterol and fasting plasms glucose were measured at baseline and at 2 years.

Analysis of results showed that during the course of the study, 14% (n=84) of the study participants had developed major depressive disorder (as per DSM-IV criteria). About 5% had developed depression even at 2-year follow up.

The risk of developing incident major depression was 89% greater in individuals with high TG:HDL ratio (≥0.83 for females and ≥1.22 for males) (HR 1.89, 95% CI 1.15-3.11). The risk was also found to be 37% higher in those with fasting plasma glucose level ≥100 mg/dL (HR 1.37, 95% CI 1.05-1.77). Similarly, pot belly obesity or “central adiposity” (waist circumference ≥ 100 cm [39 in]) was associated with 11% higher risk of depression. These associations were similar for both the male and female participants.

A secondary analysis of participants with new-onset insulin resistance within 2 years of the initiation of the study was conducted to more accurately define the onset of insulin resistance during the study. At 2-year follow up, while individuals with new-onset insulin resistance (prediabetes) had more than doubled their risk of major depression (HR 2.66, 95% CI 1.13-6.27), the association of new development of high TG:HDL ratio and increased waist circumference with depression was not significant. Even one unit change in TG:HDL ratio corresponded to an 89% increase in the rate of incident major depressive disorder during the 9-year follow-up period.

The association between diabetes and depression is well-recognized. People with diabetes are 2 to 3 times more likely to have depression than people without diabetes, as per CDC. Only 25% to 50% of people with diabetes who have depression get diagnosed and treated.

However, this study has linked insulin resistance with depression. TG:HDL-C ratio, fasting plasma glucose and central adiposity are markers of insulin resistance. All three were found to increase the risk of a major depressive disorder in this study suggesting that even persons with prediabetes are likely to develop depression.

Hence, in view of the association of insulin resistance with depression, all persons with diabetes, prediabetes, hypertension or even obese individuals should be tested for insulin resistance to predict their risk of developing depression. Natalie Rasgon, MD, PhD, Stanford and coauthor of the study said, "To prevent depression, physicians should be checking their patients insulin sensitivity. These tests are readily available in labs around the world, and theyre not expensive."

Reference

1. Watson KT, et al. Incident major depressive disorder predicted by three measures of insulin resistance: a Dutch cohort study. Am J Psychiatry 2021; DOI: 10.1176/appi.ajp.2021.20101479.