4th Apr 2023
Research indicates that eating disorders have a genetic component. But, like all human behaviors, eating disorders aren’t solely due to genetics and are instead the result of a combination of factors.
Anorexia nervosa is, in part, the result of genetics. Previous studies show that females with a relative who has anorexia are 11 times more likely to develop anorexia themselves. However, family studies don’t provide a complete picture because first-degree relatives share both genetics and environmental experiences.
Twin studies help control this variable by comparing monozygotic and dizygotic twin pairs. Monozygotic twins have identical genetics, while dizygotic twins share half of their genetics. A higher correlation of anorexia between monozygotic twins versus dizygotic twins indicates a genetic influence.
Researchers have found such genetic correlations. In fact, some studies indicate that as much as 76 percent of the variance of liability of anorexia is related to genetics. It’s important to note, however, that not all twin studies on anorexia have determined such a high degree of genetic liability.
Nonetheless, the consensus is that anorexia has moderate heritability traits. As new and emerging research methods delve into the causes of anorexia, this assumption seems to gain more traction. For example, a study by the Psychiatric Genomics Consortium notes that anorexia is potentially related to a genome-wide locus on the twelfth chromosome.
Current and future research aims to investigate this genetic link even further. One such genetic study by the Eating Disorders Genetics Initiative (EDGI) - which is collecting data from volunteers at the time of writing - hopes to collect genetic information from at least 100,000 people with and without an eating disorder. Comparing the genetic material of these two groups might lead researchers to identify more specific genetic markers that indicate the propensity for developing anorexia.
Like anorexia, bulimia nervosa is caused in part by genetic risk factors. Familial studies show a seven to twelve-fold increase in bulimia if one has a first-degree relative with the disorder. But, again, twin studies are necessary to shed more light on the strength of the genetic component of this disorder.
Twin studies indicate the potential variance in the genetic liability for bulimia to be anywhere from 54 to 83 percent - even higher than anorexia. However, much less is known about the genetic causes of bulimia than anorexia, so these estimates must be viewed cautiously.
Researchers haven’t yet identified specific genetic loci for bulimia (and have only identified a handful for anorexia). To put this in perspective, more than 200 loci have been identified for schizophrenia. This demonstrates how far research has to go in identifying the specific genetic factors underlying the development of this disorder.
Nevertheless, mental health researchers are confident that genetics plays a part. The results of the EDGI study described earlier may shed significant light on the specific genetic factors involved in the development of bulimia. That study can also help clarify questions like “Can eating disorders be genetic?” and “Are eating disorders hereditary?” by examining both genetic and environmental influences on the development of this disorder.
Binge eating disorder wasn’t identified as a disorder until the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) was published in 2013. As such, far less research exists on this disorder than on anorexia and bulimia.
However, despite limited studies of this disorder, it appears as though a genetic component exists. Twin studies reveal heritability estimates in the 0.39 and 0.45 range, which indicates moderate heritability of the disorder.
Likewise, researchers believe that binge eating disorder might be related to genes responsible for the myelination of nerve fibers in the brain. In addition, researchers have identified that the cytoplasmic FMR1-interacting protein 2 is a primary genetic marker for the development of this disorder.
In addition to genetics, other causes of eating disorders have been identified over the years. These range from environmental influences and childhood trauma to comorbidity with other psychiatric disorders. These potential causes are outlined below.
Environmental factors have been heavily studied for years as a primary risk factor for eating disorders. A prime example is the ideal of the perfect body shape and size often found in the media, particularly those aimed at women.
A component of this is undoubtedly peer pressure (especially during the teen years) to look a certain way. Young women, in particular, may feel extreme pressure to conform to popular beauty trends, some of which might promote a specific look that is both difficult to achieve and perhaps even unhealthy. These influences don’t just affect girls and women, either, and pose a risk for boys and men as well.
Additionally, research shows that environmental influences in the home might be involved in the development of eating disorders in children. For example, studies show that parents of children with eating disorders often display personality traits associated with eating disorders. This might include an obsession with exercise, a focus on appearance, and disordered eating habits.
Moreover, researchers have found that women with eating disorders might have exaggerated concerns about their children’s weight. This may even occur when the child’s weight is within the normal range of appropriate weight for their age. For example, 20 percent of mothers with eating disorders report trying to change their child’s appearance.
This is in no way to suggest that the development of an eating disorder in a child is the fault of a parent or caregiver. Instead, these examples illustrate the power of the environment in shaping human behavior.
Childhood traumas, ranging from emotional abuse to sexual abuse to bullying, among others, might be a factor in developing eating disorders later in life.
In fact, research shows that people with an eating disorder are more likely to report adverse childhood experiences than the average. More specifically, women with an eating disorder are more likely to have been sexually abused. Higher incidences of family dysfunction are also more common among people with an eating disorder than the average population.
Another common risk factor that might predict an eating disorder is having a comorbid mental health condition. The most common disorders that co-occur with eating disorders include:
Furthermore, research indicates that suicidal ideation, self-injurious behaviors, and sexual dysfunction frequently co-occur with eating disorders. Estimates are that 55 percent or more of people with a diagnosed eating disorder also have a diagnosis for one or more other mental health disorders.
This is not a complete list of all the potential causes of eating disorders but merely a sample of some of the most common risk factors. Many other factors may be involved, some of which are unknown.