Is anorexia nervosa genetic?

Anorexia nervosa is disordered eating that affects millions of people worldwide. Its impact on physical and mental health has led researchers to delve into the question: Is anorexia genetic?

Recent studies have uncovered strong evidence suggesting a genetic component to anorexia. Scientists have identified specific genes and chromosomes that may increase a person’s risk of developing the condition. This research has an impact on how we approach the treatment and prevention of anorexia. Additionally, it offers new insights into the symptoms of anorexia and its connection to other mental health and psychiatric disorders, paving the way for more targeted and effective treatment.

Defining anorexia nervosa

The American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) provides the clinical criteria for diagnosing anorexia nervosa. The key elements include:

• Restriction of energy intake relative to requirements, leading to a significantly low body weight
• Intense fear of weight gain or becoming “fat,” even when the individual is underweight
• Disturbance in the way one’s body weight or shape is experienced, undue influence of body weight or shape on self-evaluation, or persistent lack of recognition of the seriousness of the current low body weight

The role of genetics in anorexia

This complex eating disorder has a strong hereditary component, with studies showing significant genetic contributions to the risk of developing the condition.

Twin and family studies

Twin and family studies have been very important in uncovering the genetic basis of anorexia. These studies have demonstrated that the disorder runs in families. First-degree relatives of individuals with anorexia have a higher likelihood of developing an eating disorder compared to those without a family history. Twin studies, which compare identical and non-identical twins, have also confirmed the strong genetics of anorexia.

Heritability

Heritability estimates for anorexia nervosa vary across studies but generally indicate a deep genetic component. Research has found that genetic influences account for approximately 50-60% of the risk of developing anorexia. This means that genes have a significant impact on a person’s susceptibility to the disorder. However, it’s important to note that heritability doesn’t guarantee the development of anorexia, as environmental factors also play a role.

Gene-environment interactions

The link between genes and environment is important in understanding the development of anorexia. While genetic factors increase susceptibility, environmental triggers often play a part in the start of symptoms. For instance, individuals with a genetic predisposition might be more vulnerable to pressures regarding body image or weight. This gene-environment interaction helps explain why some people with genetic risk factors develop anorexia while others do not.

Genes linked with anorexia

Genetic research has identified several genes that may have an impact on a person’s susceptibility to anorexia. These genes are involved in various biological processes, including neurotransmitter function and weight regulation can interrupt pathways. Understanding these genetic factors helps shed light on the question: Is anorexia genetic?

Serotonin genes

Serotonin plays a crucial role in regulating food intake, mood, and anxiety. Studies have focused on genes involved in serotonin neurotransmission, such as the 5-HTR2A gene.

Dopamine genes

Dopamine has a part in regulating emotions, motivation, and motor activity. Research has examined dopamine receptor genes, including DRD2 and DRD3. Some studies have reported that anorexia patients carrying a particular DRD3 genotype showed higher scores on various eating disorder scales.

Genes involved in weight regulation

Recent genome-wide association studies have identified genes that may influence both anorexia risk and body weight regulation. One such gene is PTBP2, which has been linked to both anorexia nervosa and body mass index. This gene’s expression levels have been found to differ between individuals with obesity and those of normal weight, suggesting a role in weight regulation.

Genetic overlap with other disorders

Research has uncovered significant genetic overlap between anorexia nervosa and other mental health conditions.

Anxiety and depression

Studies have shown that anorexia nervosa often co-exists with depression and anxiety disorders. This overlap has a genetic basis, with research indicating that the genes increasing the risk for anorexia might also contribute to the development of these mood disorders. The genetic correlation between anorexia and major depressive disorder is particularly strong.

Other eating disorders

While genetic studies on bulimia nervosa and binge eating disorders are less extensive, some evidence points to shared genetics across various eating disorders. Some researchers propose a model where all eating disorders share common genetic factors, with differences in gene expression accounting for the variations in behaviour. For instance, mutations in the same gene could lead to food restriction in one individual (anorexia) or indulgence in another (bulimia or binge eating disorder).

Personality traits

Certain personality traits associated with eating disorders have been found to have a genetic link. These highly heritable traits often exist before the start of the eating disorder and may contribute to its development. They include obsessive thinking, perfectionism, sensitivity to reward and punishment, emotional instability, and rigidity.

Treatment and prevention

The genetic component of anorexia has a significant impact on treatment and prevention strategies. Understanding the genetic factors involved helps healthcare professionals develop more targeted approaches to address this complex disorder.

Personalised medicine

This approach takes into account an individual’s genetic makeup to tailor treatment. For instance, molecules targeting specific genetic pathways could help curb harmful eating impulses. However, developing and testing these drugs will take time. In the meantime, current treatments, while not based on genetics, have helped many people overcome harmful eating patterns and develop healthier lives.

Early intervention

Recognising the genetic risk factors for anorexia allows for early intervention. Identifying individuals at high risk for a chronic eating disorder at an earlier stage could lead to more tailored treatments. Early, timely access to intervention can shorten the duration of untreated eating disorders, helping to prevent prolonged illness. Studies suggest that intervention within the first three years of illness offers a greater likelihood of recovery.

Genetic counselling considerations

Genetic counselling may become an important tool in managing anorexia. As we learn more about the genetic factors involved, counsellors can help individuals understand their risk based on family history and genetic profile. This information could be crucial for prevention, especially in families with a history of eating disorders. It’s important to note that while genetics play a role, environmental factors also contribute to the development of anorexia. Therefore, genetic counselling with family members or alone could be part of the treatment approach that includes psychological and nutritional support.

Conclusion

Research has shown that genes have a significant influence on a person’s susceptibility to anorexia, with heritability estimates ranging from 50-60%. This genetic component interacts with environmental factors, highlighting the complex nature of the disorder. The identification of specific genes linked to anorexia, along with its genetic overlap with other mental health conditions, paves the way for more targeted treatment approaches.

Sources

• The Genetics of Eating Disorders – PMC
• How Eating Disorders Are Inherited – Science – AAAS
• A genetic link to anorexia