Insulin Resistance Doubles the Risk of Major Depressive Disorder

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Highlights:

• Depression is a real mental health disorder that affects every 1 in 5 Americans
• Almost 40% of mood disorder patients are insulin-resistant
• Moreover, the risk of major depressive disorder is found to be doubled by insulin resistance
• Hence, experts need to think through the metabolic status of those with mood disorders or vice versa

Risk of major depressive disorder is doubled by insulin resistance, as per a study at Stanford, published in the American Journal of Psychiatry.

What is Major Depressive Disorder?

Major Depressive Disorder (MDD), otherwise called depression, is a type of mental/mood disorde that is manifested by a persistent feeling of low mood/sadness or loss of interest for a minimum of at least two weeks.

In other words, melancholic feelings of grief or unhappiness. It is estimated that 1 in 5 Americans experience a major depressive disorder at least at some point in their lives.

MDD - Symptoms & Precipitating Factors

The common symptoms of MDD include the following:

• Incessant sadness, or "empty" mood
• Hopelessness or guilt feeling
• Sluggishness/loss of energy
• Pessimism
• Despair
• Loss of appetite with or without weight changes
• Sleep disturbances
• Suicidal thoughts

Precipitating factors that contribute to this debilitating disease are:

• Emotional traumas
• Childhood traumas
• Loss of a loved one
• Stresses of the COVID-19 pandemic

Understand the role of Insulin

Insulin is a hormone secreted by the cells of the pancreas (beta cells in the islets of Langerhans) to guide the body cells (through the presence of insulin receptors on them) to utilize glucose for energy.

‘Insulin resistance invites various detrimental health outcomes including several mental disorders. Hence, an insulin-resistant individual has almost double the chance of developing major depressive disorder when compared to those who are not insulin-resistant.’

Glucose is the fuel to every body cell. It is commonly stored in the liver to manage the periodic energy demands of the body. Insulin, in turn, is the master regulator of this precious energy source - glucose.

However, lifestyle-related risk factors like stress, lack of exercise, increased intake of calories, and insufficient sleep add to the development of resistance against this wonder hormone - insulin.

What is Insulin Resistance?

Insulin resistance is the inability of the body cells (liver, fat, and muscles) to respond properly to insulin and utilize glucose for energy. Consequently, the pancreas starts making more insulin, thereby resulting in increased blood sugar levels.

Data report that every one in three individuals lives with insulin resistance without even knowing it. The condition is different from Type 1 diabetes. If the blood sugar levels prevail on the chronically higher levels (above a threshold point), it may result in Type 2 diabetes.

Insulin resistance is generally diagnosed by checking blood sugar levels. However, insulin resistance is preventable and can be reduced or managed by diet, exercise, or drugs.

Insulin Resistance & Major Depressive Disorder - The Link

Insulin resistance may itself invite various detrimental health outcomes like cardiovascular and cerebrovascular disorders, kidney disease, neuropathy, limb amputations, and others.

It is established that insulin resistance is also associated with several mental disorders. Almost 40% of mood disorder patients are insulin-resistant.

Moreover, "if you're insulin-resistant, your risk of developing major depressive disorder is double that of someone who's not insulin-resistant, even if you've never experienced depression before," says Natalie Rasgon, MD, Ph.D., professor of psychiatry and behavioral sciences and the Stanford principal investigator of the study.

Analyzation of the Data

Although there is a link between insulin resistance and mood disorder, they were exclusively derived from cross-sectional studies or similar analyses of populations at a single point in time.

But, if one event was the cause or the result of the other or both were results of some other causal factor needs proper resolution. Hence, a longitudinal study (track people's health data over years to establish the reason) would help find the missing puzzle.

The present study was thereby conducted as a part of a multi-institutional collaboration with data obtained from an on-going longitudinal study (the Netherlands Study of Depression and Anxiety) that monitors more than 3,000 participants to trace out the reliable details on the causes and consequences of depression.

Study Outline

The study team analyzed data from control subjects for the Netherlands study that included 601 men and women (average age of 41 years). The participants had no history of depression or anxiety at the time of enrolment.

Three proxies of insulin resistance were measured - fasting blood glucose levels, waist circumference, and the ratio of circulating triglyceride levels to those of circulating high-density lipoprotein (HDL or "good" cholesterol).

The team anticipated examining the link of insulin-resistant in patients with a heightened nine-year risk of developing a major depressive disorder. Some of the participants were already insulin-resistant at the start of the study.

What was Revealed?

It was found that the moderate increase in insulin resistance, as stated by the triglyceride-to-HDL ratio, was associated with an 89% increase in the rate of new major depressive disorder cases.

In addition, there was a prevalence of 11% higher rate of depression for every 5-centimeter upturn in abdominal fat. And, a 37% higher rate of depression with an increased fasting plasma glucose of 18 milligrams per deciliter of blood.

Subsequent Phase

Since some of the study participants had already developed insulin resistance, the team enrolled around 400 subjects for their next phase of study, who had no signs of insulin resistance or depression at the onset of the study.

It was found that 100 participants from the total group (400) had developed insulin resistance within the first 2 years of the study. Further to this, their chance of acquiring major depressive disorder in the next seven years was also compared with those who did not become insulin-resistant within a similar time frame of two years.

Fasting Glucose Test - Predictor of MDD

The study found a significant correlation of fasting glucose with the risk of MDD. However, waist circumference and the triglyceride-to-HDL ratio were not found to be equally significant.

Thus, participants who had prediabetes within the first two years of the study revealed 2.66 times the risk of developing major depression at the nine-year follow-up when compared with those who had normal fasting-glucose test results at the two-year point.

The study thereby states that insulin resistance is a robust risk factor for several morbidities like depression (apart from Type 2 diabetes).

"It's time for providers to consider the metabolic status of those suffering from mood disorders and vice versa, by assessing mood in patients with metabolic diseases such as obesity and hypertension. To prevent depression, physicians should be checking their patients' insulin sensitivity. These tests are readily available in labs around the world, and they're not expensive. In the end, we can mitigate the development of lifelong debilitating diseases," says Rasgon, also a member of the Wu Tsai Neurosciences Institute at Stanford, Stanford Cardiovascular Institute, and the Stanford Maternal and Child Health Research Institute.

Facts on Depression

• There are several myths associated with depression-like it's just something made up in the head or being lazy, that can go away on itself.
• The truth is depression is beyond normal sadness. It is a real illness - a mental health disorder.
• It can be caused due to chemical imbalances (neurotransmitters) in the brain.
• Anybody can develop depression, even children. They are not resistant to depression.
• Hence, it is important to diagnose the disorder through its telltale signs and prevent the worst outcomes.
• Many people tend to believe that depression isn't something to be treated or can be treated. "You have to just let it go"!
• The good news is depression is completely treatable through a combination of therapies (if proper measures are taken).
• Hence, it is important to break the stigmas on depression and lend a helping hand to the ones suffering from it.

References:

1. Depression (major depressive disorder) - (https:www.mayoclinic.org/diseases-conditions/depression/symptoms-causes/syc-20356007)
2. Major depressive disorder, single episode, unspecified - (https:www.icd10data.com/ICD10CM/Codes/F01-F99/F30-F39/F32-/F32.9)
3. Depression - (https:www.nimh.nih.gov/health/topics/depression)
4. Insulin Resistance & Prediabetes - (https:www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance)
5. Pancreas - (https:www.yourhormones.info/glands/pancreas)
6. Myths and Facts About Depression - (https:www.uofmhealth.org/health-library/ug4843)

Source: Medindia

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