An investigation into eating and anxiety disorder risk factors and genetic architecture in adolescent twin girls
Chief Investigator: Dr Kate Fairweather
Funding Amount: $74,906
Recipient: Flinders University
This project will provide crucial information of eating disorder risk during its greatest incidence period of adolescence, both at a diagnostic and symptom level, of pertinence to clinical and public health applications. Findings will (1) generate knowledge pertaining to observed co-occurrence of eating disorders and anxiety, including overlap between genetic and environmental risk factors; and, (2) identify strategic and specific targets that can maximise the success of interventions for prevention and treatment of eating and anxiety disorders.
Researchers: Kate Fairweather, Tracey Wade, Ben Harrison, Clara López-Sola
Research Completed: 2021
Research Findings: Eating Disorders (ED) are serious mental illnesses with substantial harmful effects on psychological and physical health. Anxiety Disorders (AD) are also debilitating conditions and also relatively common in the general population. Both disorders have their onset period earlier in life. Proportionally, more females suffer ED and AD, and are simultaneously more likely to have other psychological disorders (e.g., depression/suicidality). This study investigates whether a common genetic vulnerability connects ED and AD, using sophisticated statistical methods with twin data.
Eating Disorders (ED) are serious mental illnesses that have a substantial harmful effect on both psychological and physical health, particularly as onset commonly occurs in late childhood and adolescence. ED, particularly anorexia nervosa (AN), have one of the highest rates of medical complications of any psychiatric disorder. Those with ED are significantly more likely to die from any type of condition compared to non-affected individuals. In particular, the annual death rate due to all causes of death of among females with AN who are aged 15-24 is 12 times the rate of deaths in the general population. Suicide rates are also significantly elevated for people with certain types of ED (after accounting for age and gender differences), resulting in ED having one of the highest mortality rates across all psychiatric disorders.
Anxiety Disorders (AD) are also debilitating conditions and relatively common in the general population (prevalence for combined anxiety disorders is approximately 17%), which, like ED, have an early peak onset period early in life (i.e., childhood and adolescence/early adulthood). The highest proportion of sufferers are female who frequently have other psychological disorders simultaneously (e.g., anxiety, depression, suicidality). Some hypothesise that this “comorbidity” is driven by cognitive factors present in both those with ED and AD, such as perfectionism, fear of negative evaluation, and/or avoidance of strong emotion. A trait-like risk factor, Anxiety Sensitivity (AS), has characteristics that are present in both ED and AD. While AS functions like a personality characteristic (typically consistent over time and context), it has been shown to respond to interventions, and reduce in symptoms of anxiety. Because of this capacity for change, AS represents an excellent candidate to research using a series of biometric twin models. These models allow us to investigate whether an underpinning genetic vulnerability connects both AS and ED symptom profiles. Benefits of the funding support from Ch7CRF reside in determining if significant a connection exists, and if so, we can focus our energies on developing interventions that may ameliorate AS, potentially reducing the incidence of ED in young people.
Results and Discussion:
Study 1 –
Despite established comorbidity between anxiety and sub-clinical eating problems (termed “disordered eating”; DE), and a large body of research using various methodologies to examine this overlap, use of twin modelling to expose whether a shared genetic link underlies these conditions remains rare. Our study identified that both genetic and environmental influences (including stressful events like teasing) are likely to account for this relationship, and potentially the observed comorbidity between anxiety sensitivity and DE. As the age of onset is typically earlier for anxiety than DE, it presents a significant opportunity for early intervention work to reduce subsequent development of DE.
Study 2 –
Suicidality co-occurs with both anxiety disorders and eating disorders. One prominent perspective maintains that greater severity of each respective diagnosis independently leads to suicidal outcomes. An alternative viewpoint suggests that an underlying genetic link provides a heritable risk which connects the two disorders. Thus, we sought to investigate whether a heritable characteristic, represented by suicidal symptomatology, constituted a genetic link uniting anxiety and eating disorders. Result suggested the heritability of suicidality is shared significantly with the heritability of anxiety disorders and eating disorders. Findings highlight future research should focus on detangling the specific observable behavioural/emotional characteristics that account for this relationship (e.g., emotion regulation difficulties) that can then be targeted by specific interventions.
Study 3 –
Studies suggest that anxiety (particularly anxiety sensitivity) constitutes a risk factor for eating psychopathology, or that both conditions may be manifestations of an underlying heritable vulnerability, such as emotional regulation/reactivity. Ultimately, however, the observed condition is likely to be dependent on the action of specific environmental factors, such as childhood adversity/trauma. We also know that parent anxiety sensitivity is linked to child anxiety, but current analytic methodologies have made it difficult to determine if this is due to genetics or the influence of the shared context within which the family operates and resides. Nevertheless, one such analysis, termed nuclear twin family modelling, uses a combination of parents of twins’ and twins’ data to tease apart the influence of these contributions to anxiety sensitivity symptomatology. This constitutes the final study generously funded by the Channel 7 Children’s Research Foundation.
This exciting group of studies underscore two important and widely impacting outcomes.
First, it shows there is great value of considering/addressing psychological conditions in terms of: a) underlying similarities shared by other psychological disorders, termed the transdiagnostic approach (which assists development of more flexible and adaptive therapeutic approaches); and that, b) highlighting a dimensional/continuum approach is likely to be more effective in addressing psychological problems owing to the benefits of prevention and early intervention (as opposed to delaying until symptoms are considered “clinical”). This is particularly pertinent for ED and AD, as these are conditions arising earlier in life, which can become chronic, seriously curtailing personal, social and economic life-engagement. Second, these studies highlighted clear genetic links between psychological conditions and degrees of heritability. Further, our previous research suggests certain environmental triggers appear to “switch on” these genetic predispositions (e.g., childhood trauma, including body weight-focused teasing/bullying). By recognising differences in ages of onset of linked disorders (e.g., anxiety symptoms typically emerge early in childhood) and the types of personal experiences that may trigger a related disorder (e.g., ED) there is potential to reduce future risk of developing a psychiatric diagnosis.
Papers (published, submitted & in preparation):
- A.K. Fairweather-Schmidt & T. D. Wade. (2020). Does common genetic architecture and environmental risk factors underpin the anxiety-disordered eating relationship? Findings from an adolescent twin cohort. International Journal of Eating Disorders, 53(1):52-60. doi: 10.1002/eat.23155. Q1, SJR=1.522. (Published)
- A.K. Fairweather, T. D. Wade, G. Zhu, & N. Martin (2021). Is a genetic diathesis represented by suicidal phenotype implicated in the co-occurrence of anxiety and eating disorders? Psychological Medicine (Submitted 18/05/21).
A.K. Fairweather, T. D. Wade, & M. Zyphur (2021). Anxiety Sensitivity: genes or environment? A nuclear twin family analysis of adolescent female twins and their respective parents. Psychological Medicine (in preparation).