How Do Genes Influence Eating Disorders and Anxiety in Children and Teens?

What you need to know

• Genetic risk for anorexia nervosa and obsessive-compulsive disorder (OCD) may predict eating disorder and anxiety symptoms in children and adolescents.
• The influence of genetic risk differs between boys and girls and changes with age.
• Compulsive exercise may be an important shared symptom between anorexia and OCD with genetic links.

Understanding genetic risk scores

To understand this research, it’s helpful to know about genetic risk scores. Our genes contain instructions for how our bodies and brains develop and function. Some genetic variations are associated with increased risk for certain health conditions or traits.

Scientists can look at a person’s overall genetic profile and calculate a “polygenic score” that estimates their genetic risk for a particular condition, like anorexia nervosa. A higher polygenic score suggests a higher genetic predisposition, though it doesn’t guarantee someone will develop the condition.

This study used polygenic scores for anorexia nervosa and OCD to see if they could predict eating disorder and anxiety symptoms in children and teens. The researchers also combined the anorexia and OCD genetic information to create a “transdiagnostic” score, to capture shared genetic risk between the two conditions.

Key findings in girls

In girls, genetic risk for anorexia nervosa predicted several eating disorder-related outcomes at age 14:

• Higher likelihood of having a threshold or subthreshold eating disorder
• Higher rates of eating disorders not otherwise specified or purging disorder
• More compulsive exercise behaviors

The combined anorexia/OCD genetic score also predicted these outcomes, as well as more fasting behaviors and feeling more pressure to lose weight.

For anxiety symptoms, anorexia genetic risk predicted higher separation anxiety at age 7. The combined anorexia/OCD score was associated with separation anxiety as well as higher levels of social anxiety and general worry at age 13.

Interestingly, genetic risk for OCD alone did not predict many of the eating disorder or anxiety outcomes in girls. However, it was associated with more compulsive exercise at age 16.

Key findings in boys

The results for boys showed some differences compared to girls. Genetic risk for anorexia predicted more emotional eating at age 14. The combined anorexia/OCD score was also associated with emotional eating.

For anxiety symptoms, anorexia genetic risk predicted more worrying at age 10 in boys. However, it predicted lower scores on some OCD-related measures at age 13.

Overall, there were fewer significant findings for boys compared to girls. This may be partly due to eating disorders and anxiety being less common in boys, making effects harder to detect statistically.

Compulsive exercise as a key shared symptom

One of the most intriguing findings was around compulsive exercise behaviors. This was the only symptom predicted by both anorexia and OCD genetic risk scores in girls.

Compulsive exercise involves a driven urge to exercise excessively, often with feelings of anxiety if unable to do so. It’s a common feature in eating disorders, especially anorexia nervosa. This study suggests it may have genetic links to both eating disorders and OCD.

The researchers note that compulsive exercise encompasses hallmark symptoms of both anorexia (like weight/shape concerns) and OCD (compulsive behaviors). Clinically, individuals with anorexia who also have compulsive exercise tend to have more OCD symptoms.

This genetic connection may help explain why compulsive exercise can be such a challenging symptom to treat in eating disorders. The authors suggest more research is needed to understand the habitual and compulsive nature of exercise in eating disorders, which could lead to better targeted treatments.

Changes across development

An important aspect of this study is that it looked at symptoms at different ages, from childhood through adolescence. This revealed some interesting patterns in how genetic risk may influence symptoms over time.

For eating disorder symptoms in girls, genetic risk seemed most influential around age 14. The anorexia genetic score predicted several eating disorder outcomes at 14, but not at age 16.

For anxiety symptoms, there were effects at different ages. In girls, anorexia genetic risk predicted separation anxiety at age 7 and OCD-related symptoms at age 13. In boys, it predicted more worrying at age 10.

These developmental differences align with other research showing that genetic and environmental influences on disordered eating can shift during adolescence. It highlights the importance of considering age and developmental stage when studying these conditions.

Sex differences in genetic risk

A key finding was that genetic risk for anorexia nervosa seemed to play a larger role in predicting symptoms for girls compared to boys. This was contrary to the researchers’ initial hypothesis.

They had expected genetic risk might be more impactful for boys, since previous twin studies found higher heritability of disordered eating in pre-pubescent boys compared to girls. However, this study found more and stronger associations between genetic risk and symptoms in girls.

There are a few potential explanations for this:

1. The study may have lacked statistical power to detect effects in boys, since eating disorders are less common in males.

2. Genetic risk in boys might manifest at earlier ages than were measured in this study.

3. Disordered eating in boys could be more influenced by genetic factors for other conditions not measured here.

4. There may be sex differences in how genetic risk translates into observable symptoms.

These results highlight the need for more research on sex differences in the development of eating disorders and related symptoms.

Conclusions

• Genetic risk for anorexia nervosa and OCD can predict some eating disorder and anxiety symptoms in children and adolescents.
• These genetic influences appear to differ between boys and girls and change across development.
• Compulsive exercise may be a key shared symptom between anorexia and OCD with genetic underpinnings.
• More research is needed to understand sex differences in how genetic risk influences symptom development.

This study provides new insights into the complex relationships between genetics, eating disorders, and anxiety. By looking at how genetic risk relates to specific symptoms across childhood and adolescence, it may help identify children at higher risk who could benefit from early intervention. It also points to potential shared biological pathways between eating disorders and anxiety that could inform new treatment approaches.

However, it’s important to remember that genetic risk is just one piece of the puzzle. Environmental factors, life experiences, and individual choices also play major roles in whether someone develops an eating disorder or anxiety condition. A higher genetic risk score does not mean these conditions are inevitable. Rather, this type of research helps us better understand the underlying biology to ultimately improve prevention and treatment.