Why Is Anorexia a 'Metabo-Psychiatric' Illness?

Eating disorders are known as one of the United States' most prevalent mental health conditions. But recent research suggests they may have both psychiatric and biological underpinnings, some of which are genetic.

In the first part of this story, we began discussing what has been uncovered following years of genetic studies. Now, we'll get into why eating disorders are now considered "metabo-psychiatric" illnesses, and what that means for treatment and prevention.

Research into anorexia nervosa

"At this point, our most important finding is that anorexia nervosa appears to have both psychiatric and metabolic underpinnings," said Cynthia Bulik, Ph.D., founding director of the Center of Excellence for Eating Disorders at the University of North Carolina School of Medicine in Chapel Hill. "We showed this by correlating the genetic profile of anorexia with hundreds of other traits."

Anorexia nervosa, according to the research, was highly positively genetically correlated with the following conditions:

• OCD [obsessive compulsive disorder]
• Depression
• Anxiety
• Schizophrenia

That places it squarely within the psychiatric category, Bulik added. But it was negatively correlated conditions such as:

• Type 2 diabetes
• Insulin resistance
• BMI (body mass index)
• Obesity

Those findings suggested to the researchers that some of the same genes that increase the risk of developing anorexia nervosa decrease the risk of developing obesity, type 2 diabetes, etc.

New thinking toward anorexia

As a result, many experts today think of eating disorders as "metabo-psychiatric illnesses," which are biological and psychological in nature.

"This might explain, in part, why certain people with anorexia sometimes repeatedly return to an extremely low weight or experience co-occurring mental health conditions, such as OCD, anxiety and depression," said Samantha DeCaro, Psy.D., a Philadelphia-based therapist and director of clinical outreach and education for The Renfrew Center. "There is a danger, however, in assuming all people with anorexia will have a genetic tendency to be lower weight.

"Anorexia is a set of symptoms that can affect all shapes and sizes, and the restriction of intake can cause severe medical and psychological complications regardless of body weight. Research studies suggest that the duration of anorexia symptoms seems to be a much better predictor of severity compared to body weight."

In addition to metabolism, body composition and related characteristics, genes can influence a person's psychological makeup and personality, all of which can diminish or raise a person's risk of developing an eating disorder. However, most experts believe these conditions and traits are a result of a combination of factors—psychiatric, metabolic, or based on personality or environment—and not genes alone.

Psychiatric factors

Eating disorders frequently co-occur with other mental health conditions, such as depression, anxiety and OCD, and neurological differences, such as autism and ADHD, according to Bulik and DeCaro. Experts aren't sure what causes most mental health conditions and neurological divergences, but most agree they are likely multifactorial. Some, though not all, of these conditions are thought to be hereditary.

Research suggests people who have experienced trauma, especially childhood abuse, are more susceptible to eating disorders. In particular, people who have experienced childhood sexual abuse are at significantly higher risk of bulimia and binge eating disorder. According to the National Eating Disorders Association (NEDA), historical trauma, or intergenerational trauma, which is thought to be heritable, can contribute, too.

Other psychological characteristics that can increase a person's vulnerability to eating disorders, according to research, include:

• Stress
• Low self-esteem
• Poor body image
• Bullying
• Societal or peer pressure

Receiving critical comments or messages about appearance, eating habits and weight can also predispose a person.

Metabolic factors

The work of Bulik and other researchers suggests that metabolic disorders, which can be heritable, are common in people with anorexia. These irregularities can intercept neurological pathways involved in several hormones and receptors.

Cannabinoid receptors

Cannabinoid receptors are part of the endocannabinoid system, which spans the brain and body and influences everything from digestion and reproduction to mood and energy. Malfunctions can affect multiple systems and processes, including metabolism, hunger and hormones.

Hormones

Hormones such as ghrelin and leptin regulate energy, appetite and satiety. An imbalance can contribute to food aversion—in the case of anorexia or ARFID (avoidant restrictive food intake disorder)—or increased hunger. Imbalances can also affect fullness cues.

Serotonin and dopamine

Serotonin affects appetite, mood, satiety, anxiety and sleep. Dopamine helps to regulate motivation, emotions and motor activity. Imbalances between these two neurotransmitters can contribute to eating disorders, mental health conditions, and weight gain or loss.

Vitamin D3

This nutrient helps to regulate sex hormones, support the immune system and facilitate calcium absorption. People with vitamin D3 deficiencies are more likely to experience fatigue, depression and metabolic issues, as well as anorexia, obesity and diabetes.

"This can help us understand why individuals with anorexia nervosa are able to attain such low weights in the first place and, more importantly, why they are so vulnerable to negative energy balance [expending more than you are consuming]," Bulik said. "Even individuals who have recovered from anorexia nervosa have to be very careful about falling into negative energy balance because it can precipitate a relapse."

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More About Recognizing an Eating Disorder

• Recognize the Warning Signs: Everyone’s experience is unique, but most don’t become ill overnight. Recognizing the red flags can help you get support before it’s too late.
• It’s Not Just About Your Weight: Despite the stereotypes, not everyone with eating disorders—including anorexia—is thin.
• The Truth About Male Eating Disorders: Men are often overlooked or outright dismissed when seeking care for eating disorders. The result can be life-threatening.

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Personality factors

Research indicates eating disorders, and the genetic variations that accompany them, are associated with certain personality traits, according to NEDA. Like eating disorders, personality traits are thought to be a result of environmental and biological factors, including genetics.

For example, genetic variations can influence how a person's brain processes dopamine—a neurotransmitter involved in reward response—and difficulty with dopamine regulation correlates to higher levels of novelty-seeking and impulsivity.

Generally, eating disorders are affiliated with traits such as obsessive thinking, perfectionism, hypersensitivity and emotional dysregulation. These typically precede the disorder's development.

One study published in the American Journal of Psychiatry found that many people with anorexia or bulimia had possessed one or more of five obsessive-compulsive personality traits since childhood.

Each trait—perfectionism, rule-driven, drive-for-order and symmetry, inflexibility, and excessive doubt and cautiousness—increased a person's likelihood of developing an eating disorder by about seven times. People with all five traits were about 35 times more likely to have an eating disorder than someone with none of the traits.

According to NEDA, other research suggested people with anorexia, bulimia and binge eating disorder possess high levels of harm avoidance, characterized by worry, pessimism and shyness.

Eating disorders and personality traits

Additionally, different disorders are linked to distinct personality traits, per NEDA. For example, research indicates anorexia is associated with neuroses and low levels of novelty-seeking, whereas bulimia is associated with higher levels of impulsiveness and novelty-seeking.

"Our personalities are shaped by our genetics and our environment. Temperament from infancy has strong genetic underpinning and there are strong lines of evidence that suggest that personality traits are highly heritable. Individuals with anorexia nervosa tend to show traits of high perfectionism, harm avoidance and obsessive compulsiveness," said Harry A. Brandt, M.D., a Maryland-based psychiatrist and the regional medical director for Eating Recovery Center.

"In the next wave of genetic research, large genome-wide association studies will hopefully help us identify the genetic variances associated with the various personality traits we see in major eating disorders."

Environmental factors

"There is clear evidence in research, including genome-wide studies, that eating disorders are heritable. However, certain environmental factors must be present to activate or deactivate those genes," DeCaro said.

These environmental factors can include sociocultural elements, such as the portrayal of beauty, body image, fitness and dieting in the media and social settings.

Research indicates unrealistic beauty standards and the idealization of thinness can adversely affect people's self-image and contribute to disordered eating and eating disorders in people of all genders. Likewise, dieting or being exposed to dieting in family and social situations can contribute to eating disorder development.

"It's estimated that 20 to 25 percent of dieters will go on to develop a clinical eating disorder and even more will struggle with disordered eating even years after their diet ends," DeCaro said.

Family dysfunction may also contribute. For example, a study published in Psychology Research and Behavior Management found teens with anorexia tend to come from homes with "interpersonal boundary problems, poor tolerance of conflicts and low levels of general satisfaction in their family."

Meanwhile, teens with bulimia frequently grew up in families characterized as "chaotic" with high degrees of conflict and low levels of flexibility or cohesion.

However, growing up in a dysfunctional or inflexible home doesn't guarantee a person will develop any kind of mental or physical health challenges, DeCaro said. Moreover, experts say that as much as family life could have an adverse effect, it can also have a positive one and be integral in eating disorder recovery.

"When families are incorrectly blamed for eating disorders, intense emotional responses can perpetuate negative cycles and interfere with their ability to support a child in recovery," she continued. "A better understanding of the multifactorial causes of eating disorders can help people with illnesses and their families to more effectively cope and recover."

How genetic research could lead to better treatments

Bulik, DeCaro and Brandt agreed on a couple of things. Understanding the genetic underpinnings of eating disorders is crucial to dispelling misinformation about these conditions. And better treatments need to be developed for people who have them.

"Genetic research will ultimately help us unravel the complex nature of eating disorders and lead to the identification of important new treatments in the years ahead," Brandt said. "Additionally, genetic findings have shifted the field from an overfocus on family, societal and sociocultural influences to a focus on the clear biological. This has helped to reduce bias and unfair stigma toward eating disorder patients that has existed for many years."

Bulik noted that genetic research can assist with predicting the course of the illness. That includes who's most susceptible and how likely they are to develop a "severe and enduring" case. Ultimately, she added, it may lead to better medications—there are currently none designed specifically for eating disorders—and personalized treatments.

"Right now, we use a one-size-fits-all approach, but there is no reason to believe that the same treatment should work for everyone," she said. "I always compare it with the treatment of hypertension. Physicians have a deep toolbox to choose from, starting with lifestyle changes and then working through several classes and combinations of medications until something works. And even then changing it if the medicine's effect starts to wane.

"Eating disorders clinicians have a very sparse toolbox. Our job is to increase the number of tools that they have and the precision of those tools to help individuals based on their illness and, possibly, genetic profile."

Reduce eating disorder risk

If you are genetically predisposed to eating disorders, DeCaro explained there are ways to reduce your risk while supporting your mental health and general well-being. Begin with avoiding diets or caloric restriction and nurturing a healthy relationship with food and your body.

"Food is more than fuel," she said. "Allow food to be a source of pleasure, culture, celebration, comfort and connection without shame or guilt attached to it.

She added it's equally important to unpack internalized weight stigma and avoid equating wellness with thinness.

"Nourishing your body, honoring cues for movement and rest, managing stress, developing positive coping strategies, finding community and seeking out mental health services can all be ways to support mental health," DeCaro said. "There are no guaranteed ways to prevent an eating disorder or any other mental health condition, so remember to offer yourself lots of grace, acceptance and self-compassion along the way."