Anorexia nervosa and generalized anxiety disorder: Further explorations of the relation between anxiety and body mass index

Abstract

We explore comorbidity of anorexia nervosa (AN) and generalized anxiety disorder (GAD) and their relation with body mass index (BMI) and evaluate the presence of fasting and excessive exercise which both have anxiolytic and weight loss effects. All participants were female: 32 with AN only, 607 with GAD only, 22 with AN and GAD (AN+GAD), and 5,424 with no history of AN or GAD (referent) from the Swedish Twin study of Adults: Genes and Environment (STAGE). Lowest adult BMI differed significantly (p < .001) and was lower in those with AN+GAD than those with AN only (p < .029). Those with AN+GAD were most likely to endorse fasting and excessive exercise, followed by women with AN only, women with GAD only, and the referent. Comorbid AN and GAD may be a particularly pernicious presentation influencing both BMI and proclivity to engage in behaviors such as fasting and exercise that serve both weight loss and anxiolytic goals.

Brain-Derived Neurotrophic Factor and Neuropsychiatric Disorders

“…Studies have revealed a strong genetic contribution to eating disorders. Given the high comorbidity of AN and BN with anxiety and depressionlike symptoms (Ivarsson et al, 2000;Thornton et al, 2011), BDNF is a gene of interest in feeding behavior and weight (Rask-Andersen et al, 2010).…”

The role of leptin, melanocortin, and neurotrophin system genes on body weight in anorexia nervosa and bulimia nervosa

“…As the illness is often protracted, low BMI and the avoidance of eating to restore healthy weight are primary factors influencing high morbidity and mortality that distinguish this illness. Low weight (and the permissive factors involved) are of interest for additional reasons as these are key aspects of AN; moreover, low body weight is the primary distinguishing diagnostic feature separating AN from bulimia nervosa (BN; American Psychiatric Association, 2013) and is associated with other clinical phenotypes, anxiety in particular (Dellava et al, 2010; Thornton et al, 2011). …”

Generalized anxiety disorder and anorexia nervosa: evidence of shared genetic variation

“…[ 1–5] Specifically, comorbidity estimates for GAD and AN have suggested up to 40% of women with AN also have a lifetime history of GAD. [1] Women with AN were more than six times more likely than women without AN to have GAD [4,6] and, conversely, women with GAD were approximately six times more likely to have AN than women without GAD. [6] Anxiety disorders tend to predate the development of AN, [2,5,7] making it likely that GAD would precede AN and biologically plausible that GAD and AN share some genetic factors.…”

“…Along with high comorbidity, the notion that GAD and AN share some common factors is supported by similar characteristics shared by women with GAD and AN. For example, it has been hypothesized that caloric restriction [6,8,9] and exercise [10,11] are anxiolytic for some individuals. Within women with AN, a relationship between high childhood anxiety and low body mass index (BMI) in the context of AN was mediated through caloric restriction.…”

“…This is supported by one study which showed women with GAD and no AN were more likely to engage in fasting and excessive exercise than women without GAD and without AN. [6] Since women with both disorder engage in similar behaviors, but to different extents, it is likely that the two disorders share some genetic and environmental features.…”