In a new study, researchers have uncovered significant connections between major depressive disorder (MDD), generalized anxiety disorder (GAD), and altered eating behaviors. The findings, published in the Journal of Psychiatric Research, provide evidence that individuals with these mood disorders are more prone to disordered eating behaviors and difficulty exercising self-control over their food intake.
The motivation behind this study stemmed from a desire to better understand the connections between mental health disorders and various physical health factors. Previous research has highlighted that mental health conditions such as MDD and GAD often coexist and can intensify each other’s symptoms. However, there was a significant gap in understanding how these conditions interact with physical health factors, particularly in relation to metabolic hormones and lifestyle behaviors such as eating and exercise.
“My research aims to identify biological markers of MDD, primarily brain patterns that indicate risk for future MDD, past MDD, and/or current MDD and potential sex differences in these patterns,” said study author Jennifer Stewart, a principal investigator at the Laureate Institute for Brain Research and an associate professor of Community Medicine at the University of Tulsa.
“My interest in this topic stems from a history of mood disorders in my extended family that appears to be more severe in female than male family members. Breanna McNaughton is a research assistant in my lab with a B.S. in Biology who asked if she could develop and test her own hypotheses focused on additional metabolic and health factors that might contribute to MDD symptoms. When Bree reviewed the literature on health/eating behaviors and blood-based markers of metabolism, she realized that despite high co-occurrence of MDD diagnoses with generalized anxiety disorder (GAD), particularly in females, there were few studies identifying how people with MDD and GAD present differently than those with MDD alone.
“Here at the Laureate Institute for Brain Research we had just finished collecting data from the Tulsa-1000 study, so we saw this as an opportunity to address Bree’s hypotheses that people with two diagnoses (MDD and GAD) may show greater alterations of metabolic markers such as leptin, insulin, and adiponectin as well as more impaired health behaviors (e.g., eating habits) than people with MDD alone, and that there may be sex differences with females showing greater impairment than males.”
The Tulsa 1000 (T-1000) project aimed to provide a comprehensive understanding of the intersection between mental and physical health. Over 1,000 participants were involved, ranging from 18 to 55 years old, drawn from local treatment facilities. These participants were a mix of healthy controls and those seeking treatment for mood, anxiety, substance, and eating disorders, providing a diverse sample for analysis.
In the study, participants were categorized into three distinct groups based on their mental health diagnoses. The first group included individuals diagnosed with major depressive disorder but without other past-year disorders. The second group included participants who had both major depressive disorder and generalized anxiety disorder, also without additional past-year disorders. The third group was the healthy controls, who did not have a lifetime diagnosis of major depressive disorder or any other past-year disorders.
Participants underwent detailed clinical interviews to ascertain their mental health status and medical assessments to evaluate their physical health. Blood draws were conducted to measure concentrations of metabolic hormones like leptin, insulin, and adiponectin. Additionally, body composition was assessed using the InBody 370 Body Composition Analyzer, which employs bioelectrical impedance analysis technology to measure elements such as body fat percentage and body mass index (BMI).
Alongside these, participants completed several questionnaires, including the Three-Factor Eating Questionnaire (TFEQ) for eating behaviors, the Eating Disorder Diagnostic Scale (EDDS) for symptoms related to eating disorders, and the International Physical Activity Questionnaire (IPAQ) for physical activity levels. These measures were selected to provide a comprehensive view of the participants’ physical and mental health status, allowing the researchers to draw connections between mood disorders and physical health factors.
Female participants consistently showed higher levels of leptin and adiponectin and greater body fat compared to males, regardless of their mental health status. However, the study did not find significant differences in these metabolic markers when comparing individuals with major depressive disorder or generalized anxiety disorder to healthy controls.
When it came to eating behaviors, the researchers found significant differences between the groups. Individuals with either major depressive disorder or both major depressive disorder and generalized anxiety disorder were found to have higher instances of disordered eating behaviors compared to healthy controls. This was evidenced by higher scores on the Three-Factor Eating Questionnaire Disinhibition scale, which measures overeating in response to stress.
Additionally, these groups also displayed a heightened sense of hunger and a greater risk for developing eating disorders, as shown by their scores on the Eating Disorder Diagnostic Scale. These findings highlight a clear connection between mood disorders and altered eating behaviors, suggesting that individuals with MDD or MDD and GAD may struggle more with regulating their food intake, potentially leading to eating disorders.
“Across sexes, people who have been diagnosed with MDD in their lifetime (either with or without comorbid past-year GAD) report difficulty controlling how much they eat and are more preoccupied with their body weight/shape than people without a history of MDD or GAD,” Stewart told PsyPost. “In addition, people with pure MDD report feeling hungry more often than people without a history of MDD or GAD, so they may be misinterpreting bodily signals as hunger. These elevated symptoms of eating disorders are evident even though MDD groups did not show altered levels of metabolic biomarkers like leptin, which is involved in hunger signaling.
“Other research suggests that the processing of internal bodily sensations, known as interoception, is disrupted in people with MDD, but at this point we do not fully understand when and how this happens. The bottom line is that for people experiencing episodes of depression, it may be common to have disordered eating patterns that should be communicated to providers for additional interventions (e.g., nutritional consult, mindfulness exercises).”
Despite the strengths of the study, including its comprehensive approach and the large participant base, there were several limitations. One limitation was the higher percentage of medicated individuals in the clinical groups, which might have influenced the results. In addition, the study primarily focused on lifetime major depression rather than current episodes, which could impact the interpretation of the results in the context of current symptom severity.
“Published research on MDD metabolic biomarkers has tended to focus on unmedicated individuals with current MDD, whereas people in our MDD group were predominantly medicated and were not required to meet criteria for current MDD, just MDD in their lifetime (so it could only be past depression),” Stewart said. “It could be that various psychotropic medications cancel out biomarker alterations that we might see in depressed individuals, and/or the alterations are stronger in people experiencing high levels of current symptoms like depressed mood and anhedonia. Again we still do not understand the mechanisms.”
The study, “Impaired eating behaviors but intact metabolic hormone levels in individuals with major depressive disorder and generalized anxiety disorder“, was authored by Breanna A. McNaughton, Kaiping Burrows, Emily Choquette, Tate Poplin, Rayus Kuplicki, Martin P. Paulus, Maria Ironside, and Jennifer L. Stewart.
