Scientists associate insulin resistance with increased risk of developing major depressive disorder

Scientists at Stanford Medicine have linked insulin resistance to an increased risk of developing major depressive disorder.

“If you are insulin resistant, your risk of developing major depressive disorder is double that of a person who is not insulin resistant, even if you have never had depression before.” said Natalie Rasgon, MD, PhD, professor of psychiatry and behavioral sciences.

More than one in five Americans will suffer from a major depressive disorder in their lifetime. Symptoms include relentless sadness, hopelessness, sluggishness, trouble sleeping, and loss of appetite. Certain factors contributing to this deeply debilitating disease – childhood trauma, the loss of a loved one, or the stress of the COVID-19 pandemic, for example – are things we cannot prevent. But insulin resistance is preventable: it can be reduced or eliminated with diet, exercise and, if needed, medication.

The researchers’ findings are described in a study published online Sept. 22 in the American Journal of Psychiatry. Rasgon shares primary authorship of the study with Brenda Penninx, MD, PhD, professor of psychiatric epidemiology at the University of Amsterdam Medical Center. The lead author of the study is Kathleen Watson, PhD, a postdoctoral researcher in Rasgon’s group.

A common but silent condition

Studies have confirmed that at least 1 in 3 of us walk around with insulin resistance, often without realizing it. The condition does not result from an impairment of the pancreas’ ability to secrete insulin into the bloodstream, as occurs in type 1 diabetes, but because of the reduced ability of cells throughout the body to take into account the order of this hormone.

Insulin’s job is to tell our cells that it’s time for them to process the glucose that floods our blood from our food intake, it’s made in our liver, or both. Every cell in the body uses glucose for fuel, and each of these cells has receptors on its surface that, by binding to insulin, signal the cell to ingest the precious source of energy.

But a growing proportion of the world’s population is insulin resistant: For a variety of reasons, including excessive calorie intake, lack of exercise, stress, and lack of sleep, their insulin receptors fail to bind. correctly to insulin. Eventually, their blood sugar levels become chronically high. Once these levels stay above a certain threshold, the diagnosis is type 2 diabetes, a treatable but incurable disease that can lead to cardiovascular and cerebrovascular disorders, neuropathy, kidney disease, limb amputations and other adverse health effects.

Associations between insulin resistance and several mental disorders have already been established. For example, about 40% of patients with mood disorders have been shown to be insulin resistant, Rasgon said.

But these assessments were based on cross-sectional studies – snapshots of populations at a given point in time. The question of whether one event was the cause or the result of the other – or whether both were the result of another causal factor – is best answered by longitudinal studies, which typically follow people for years or even longer. decades and can determine which event happened first. .