BY: Melissa Munn-Chernoff, PhD and Jessica Baker, PhD
DATE: 27 June 2017
This is the fourth and final blog post in our series about the importance of genetic research in eating disorders. If you have not checked out our other posts, you can find them here (Part 1: Overview of Genetics and Genetic Research Methods, Part 2: The Genetics of Eating Disorders, and Part 3: What We Have Learned from the Genetic Studies of Other Psychiatric Disorders).
As we have said often, understanding the genetic risk for any disorder is only one piece of the larger puzzle. Environmental risk is also important, and elucidating risk (and protective) factors for eating disorders must include an examination of both genes and environment. Even though we cannot change our genetic makeup, understanding its role in the development of an eating disorder is critical for the following reasons:
Prevention efforts should include information from both genes and environment. Although we are not there yet, knowing the genetic (and environmental) risk for an eating disorder could help identify those individuals who are most vulnerable for developing an eating disorder. Targeted prevention programs can be provided to those individuals who are most vulnerable, which are aimed at preventing an eating disorder from ever developing. Additionally, knowing that there is a genetic component to an eating disorder means that psychoeducational programs can be developed and implemented for parents with a history of an eating disorder and their children who may also be at risk for developing these serious psychiatric disorders—which is something that can be done now.
Identifying individuals at “high risk”
A single gene does not “cause” eating disorders; rather, hundreds or even thousands of genes contribute to the development of eating disorders and individuals vary in how many of those risk genes they carry. A genetic risk score (or polygenic risk score) is a weighted sum of all genes that contribute to the development of a trait and can identify individuals at higher or lower genetic risk for a trait such as eating disorders. Genetic risk scores can also be developed for other traits, such as response to particular medications or risk of eating disorder relapse. This information may augment clinical information that we use in treatment planning and delivery. Again, examining both genetic and environmental risk factors will be key in refining our prediction models, providing more accurate risk prediction models that incorporate multiple pieces of the puzzle.
Patients and family members are usually eager to understand their eating disorder. We all seek explanations for why we develop a whole array of physical and psychological problem. We have found clinically that many parents and patients benefit from genetic explanations and it helps them understand how difficult recovery can be. Just because you are at high genetic risk does not mean you cannot recover, but as Dr. Bulik often says, recovery from anorexia nervosa is “fighting an uphill battle against your biology.” So we need to give people with anorexia nervosa all of the help we can in overcoming the illness. Further, understanding how genes influence eating disorders helps explain why patients simply cannot “just eat more” in the case of anorexia nervosa or “just eat less” in the case of bulimia nervosa and binge-eating disorder and recover from their eating disorder.
Patients and their families can benefit from psychoeducation about the role that genes play in the risk for eating disorders. Understanding the role of genes can reduce stigma, decrease guilt and self-blame, and assist in understanding why recovery can be challenging. However, we need to convey accurate and understandable information in order for this science to be translated and used appropriately.
We know little about beneficial treatments for eating disorders. Identifying genes may provide new targets for pharmacological treatment. It is highly probable that one’s genetic makeup influences response to medications, which could eventually be translated into personalized pharmacological treatment plans. For example, genome-wide association studies, or GWAS, have identified genes in the dopamine pathway that influence risk of developing schizophrenia. Medications prescribed to treat schizophrenia often affect dopamine, but it was unclear why these medications were effective. The GWAS results confirmed that their effectiveness may indeed be due to their action on dopaminergic systems. Medications that target other pathways in the brain whose genes have been identified as risk factors for schizophrenia (e.g., GABA genes), are also being explored as potential treatment options. Ultimately, the choice of medication may be streamlined by genetic analysis.
Pharmacologic interventions are not the only types of treatment that can be informed by genetic research. For example, twin studies have revealed shared genetic risk between anorexia nervosa and suicidal ideation, beyond any associations with major depression.1,2 Crucial information can be gleaned from these studies for clinicians, even though specific genes cannot be identified from twin studies. These results underscore that suicidality should be closely monitored in individuals with anorexia nervosa even if there is no evidence of current or past depression. Future molecular genetic research may take this one step further and identify overlap in risk genes for anorexia nervosa and suicidality.
A comprehensive understanding of how genetic and environmental puzzle pieces fit together to influence risk for eating disorders is complex and has been described in detail elsewhere.3 We will continue working toward understanding how both genetic and environmental factors contribute to risk for and maintenance of these disorders. Additionally, we will work toward clear communication of the science for families afflicted by eating disorders.
1Thornton LM, Welch E, Munn-Chernoff MA, Lichtenstein P, Bulik CM (2016). Anorexia nervosa, major depression, and suicide attempts: Shared genetic factors. Suicide and Life-Threatening Behavior, 46: 525-534.
2Wade TD, Fairweather-Schmidt A, Zhu G, Martin NG (2015). Does shared genetic risk contribute to the co-occurrence of eating disorders and suicidality? International Journal of Eating Disorders, 48:684-691.
3Mazzeo SE and Bulik CM (2009). Environmental and genetic risk factors for eating disorders: What the clinician needs to know. Child and Adolescent Psychiatry Clinics of North America, 18: 67-82.