More Than Fat: Obesity Linked to Mental Disorders

Comprehensive study shows heightened risk of developing serious mental disorders for obese individuals

travellight/Shutterstock

Obesity can significantly increase the risk of psychiatric disorder, according to a new study of the potential causal relationship between obesity and mental health.

The association between obesity and mental health is well established, including a 2006 epidemiologic survey of U.S. adults nationwide that found an association between obesity and a lifetime diagnosis of major depression, bipolar disorder, panic disorder, and agoraphobia.

The recent study, however, was the first to uncover whether obesity increased the risk of mental disorder or vice versa. Using 17 years of patient data, researchers found obese patients were far more likely than non-obese patients to develop mental disorders as serious as schizophrenia and that obesity usually predated psychiatric disorder.

The study provides another reason to manage weight gain and offer another therapeutic direction for those suffering from mental illness, joining earlier findings that exercise has multiple benefits for mental health and that certain foods can affect mood and mental well-being.

The Study

The new study used Austria’s national data registry to analyze about 45 million hospital stays of 9 million patients with and without obesity between 1997 and 2014.

Published in Translational Psychiatry in May, it was conducted by researchers at the Complexity Science Hub Vienna and the Medical University of Vienna.

“Here, for the first time in a representative counter set, which means we show it for the whole Austrian population for a longer period of time, [we] can see that for the majority of people they first get the obesity diagnosis,” study author Alexander Kautzky told The Epoch Times.

Mr. Kautzky, a researcher within the Medical University of Vienna’s Department of Psychiatry and Psychotherapy, said he thinks the study’s biggest takeaway is that individuals diagnosed with obesity could benefit from early psychiatric screening and treatment for psychiatric comorbidities.

“The concept of which comes first, mental health or obesity, has been an ongoing challenge,” Dr. Valerie Taylor, head of the department of psychiatry at the University of Calgary, told The Epoch Times in an email. “This study both helps highlight the strong obesity mental illness link and highlights some benchmarks for timelines.”

Stratifying Austria’s registry data into seven decade-long age groups (10–19, 20–29, and so on), the researchers first compared incidence of mental health disorders in obese patients with that in non-obese patients. They then further divided the data set to evaluate sex differences.

The following eight psychiatric conditions were included in the analysis: nicotine use disorder, schizophrenia, schizoaffective disorder, depressive episode, recurrent depression, anxiety disorder, somatization disorder, and personality disorder.

Patients with diagnoses of diabetes, hypertension, or coronary artery disease were excluded from the data set.

All psychiatric disorders examined, with the exception of schizoaffective disorder and schizophrenia, more commonly developed in patients after they received an obesity diagnosis. This relationship challenges the commonly held assumption that weight gain caused by psychopharmacological medications is responsible for the association between obesity and mental disorders.

Women are generally twice as likely to suffer from depression or anxiety as men are, and the study found that an obesity diagnosis worsened these trends. Depression rates were three times higher in obese women (13.3 percent versus 4.8 percent in female patients without obesity) compared with doubled rates in obese men (6.6 percent versus 3.2 in male patients without obesity).

Younger obese men (ages 20–39) had a higher risk of developing schizophrenia or schizoaffective disorder than their female counterparts, but this trend reversed for older obese patients (ages 40–79).

Obese men were more likely to develop a nicotine use disorder than obese women, with the highest occurrence rate of almost 17 percent found in patients ages 40–49. In comparison, the highest occurrence rate observed in women was about 8.5 percent.

Dr. Taylor emphasized that while the obesity diagnosis is often made first, it can’t be assumed that it precedes mental illness. She said that a cohort study in which retrospective analysis evaluates whether there was a mental illness before an obesity diagnosis could provide clarity.

The Dangers of Obesity to Mental Health

More than 1 billion people worldwide are obese.

While 1 in 4 people is estimated to have a psychiatric disorder, an obesity diagnosis increases those odds significantly. According to a 2013 study, 2 in 5 obese people have at least one psychiatric disorder, though not all are affected equally.

Women with a high BMI are more likely than men with a high BMI to suffer from major depression, suicide attempts, or suicide ideation, according to a 2011 study. Obese women are also more likely to have mood and eating disorders than obese men.

A Possible Explanation

The study wasn’t looking to explain why obesity contributed to mental illness, but Mr. Kautzky said that previous research suggests that inflammation of adipose tissue contributes to the relationship.

Adipose tissue, or body fat, triggers low-grade chronic inflammation, essentially a misfired immune response. This mechanism has also been linked to other serious illnesses.

One meta-study looked at the pro-inflammatory marker called tumor necrosis factor (TNF)—a cytokine, or immune system signal cell, that is linked to insulin resistance. The study found that TNF, which is linked to obesity-induced Type 2 diabetes, is found at elevated levels in patients with major depression. But Mr. Kautzky cautioned that inflammation isn’t a perfect explanation, since it only appears in some obese patients.

Mr. Kautzky also discussed social and economic factors that contribute to the complex relationship between obesity and mental health. He said obese people are often stigmatized, which can lead to depression or other psychiatric disorders. An example is not being selected for a job on the basis of one’s weight, an adverse experience that could feed into, for example, developing depression. He also cited low economic status, which lowers a person’s capacity to live a healthy lifestyle, as a risk factor for developing both obesity and a mental health disorder.

Obesity Treatments for Both Mind and Body

The authors concluded their study with recommendations to screen patients for mental disorders at the time of an obesity diagnosis. “Routine screenings for depressive episodes, anxiety and somatization, psychosis-spectrum such as schizophrenia and schizoaffective as well as personality disorders are called for whenever establishing a diagnosis of obesity,” they wrote.

Mr. Kautzky predicted that early psychiatric screening will lower health care costs. “Most of these patients end up as psychiatric patients anyway,” he said. “If we would be able to identify the risk earlier and prevent it from happening, most likely it would be a positive economic equation.”

Kautsky suggested that while doctors should generally refer obese patients to a psychiatric specialist, milder cases may be mitigated via self-help and other low-threshold interventions. These include community-based programs with minimal requirements for participation.

The findings also give further incentive to fund health care programs that support lifestyle changes that can arrest obesity and mental illness by promoting healthy physical activity and lower-calorie, nutrient-dense diets.