Medical instability in typical and atypical adolescent anorexia nervosa: a systematic review and meta-analysis

Abstract

This review investigates the relationship between weight and risk of medical instability (specifically bradycardia, hypotension, hypothermia, and hypophosphatemia) in adolescents with typical and atypical anorexia nervosa. Atypical anorexia nervosa, listed as an example under the DSM-5 category of Other Specified Feeding and Eating Disorders (OSFED), describes patients who are not clinically underweight but otherwise meet criteria for anorexia nervosa. There is a lack of empirical evidence exploring medical complications in adolescents presenting with atypical anorexia nervosa. The small number of studies that do exist in this area indicate that medical instability exists across a range of weights, with weight loss being associated with increased medical risk, independent of underweight. The aim of this review was to collate and analyse results from available studies and identify indicators of medical risk in these two groups of adolescents with restrictive eating disorders. Studies were identified by systematic electronic search of medical databases, including PubMed and EMBASE. All studies investigated the relationship between weight and medical instability and included adolescents diagnosed with anorexia nervosa or atypical anorexia nervosa. One randomised controlled trial, five cohort studies and three chart reviews were included, with a total sample size of 2331 participants. Between 29 and 42% of participants presented with medical instability requiring hospitalisation, in the absence of underweight. Underweight adolescents were significantly more likely to have lower blood pressures (p < 0.0001) and bradycardia was significantly associated with greater weight loss (p < 0.05). There were no statistically significant associations found between degree of underweight and heart rate, temperature, or rate of weight loss (p = 0.31, p = 0.46 and p = 0.16, respectively). Adolescents that were less than 70% median body mass index were significantly more likely to have hypophosphatemia (p < 0.05). The findings of this review support the hypothesis that medical instability can occur across a range of weights in adolescent eating disorders, with rapid weight loss being an important indicator of increasing medical risk. Results were limited by the small number of existing studies that contained data for statistical analysis. Rapid weight loss should be considered as an important indicator of medical instability in adolescents presenting with both typical and atypical anorexia nervosa.

Premorbid body weight predicts weight loss in both anorexia nervosa and atypical anorexia nervosa: Further support for a single underlying disorder

“…Patients with atypical AN represent those who develop the eating disorder following less weight loss upon adjustment for age, height, illness duration, and premorbid weight. In combination with the lack of empirical support for clinically relevant differences in psychological and medical characteristics between diagnoses (Billman Miller et al, 2024;Brennan et al, 2023;Johnson-Munguia et al, 2024;Walsh et al, 2023), we interpret our findings as further support for a homogenous illness model. We believe this interpretation represents the most parsimonious explanation for currently available data.…”

“…The heterogeneous model of AN and atypical AN has notable shortcomings, including an extant research base illustrating generally similar psychological and medical characteristics in both illnesses (Brennan et al, 2023;Johnson-Munguia et al, 2024;Walsh et al, 2023). Thus, differentiating diagnoses with a 'significantly low body weight' has not been externally validated.…”

Comparisons between atypical anorexia nervosa and anorexia nervosa: Psychological and comorbidity patterns

“…Notably, this study did not include measures of physiological symptomology. Existing studies have found that physiological symptoms or medical instability occur both among individuals with atypical AN and AN (Brennan et al, 2023;Sawyer et al, 2016). Future research should include such measures to more comprehensively identify potential differences among individuals with these diagnoses.…”

Differentiating anorexia nervosa and atypical anorexia nervosa with absolute weight cut‐offs results in a skewed distribution for premorbid weight among youth

“…'underweight,' particularly in light of growing support for a homogenous illness conceptualization (e.g., Walsh et al, 2023), may inadvertently reinforce longstanding misconceptions about restrictive eating disorders (e.g., Harrop et al, 2021). Despite comparable and potentially life-threatening symptoms (Billman Miller et al, 2024;Brennan et al, 2023;Chew et al, 2023;Garber et al, 2019;Johnson-Munguia et al, 2024;Sawyer et al, 2016;Whitelaw et al, 2018;Zanna et al, 2021), individuals with atypical AN experience myriad treatment barriers compared to patients with AN, purportedly reflecting a society permeated with weightrelated stigma (Ali et al, 2017;Eiring et al, 2021;Harrop et al, 2021;Kastner et al, 2021;Kennedy et al, 2017;Kons et al, 2024). Historically, AN has been synonymized with 'underweight,' with patients described with 'extreme emaciation' or 'inanition' dating back to the mid-19th century (Gull, 1997;Lasègue, 1997).…”

“…Patients with atypical AN consistently demonstrate similar or more severe eating disorder psychopathology (Chew et al, 2023;Garber et al, 2019;Johnson-Munguia et al, 2024;Sawyer et al, 2016;Swenne, 2016), psychiatric comorbidities and associated impairment, quality of life, adverse life events, and suicidality compared to patients with AN (Billman Miller et al, 2024;Chew et al, 2023;Johnson-Munguia et al, 2024;Zanna et al, 2021). Youth with atypical AN also demonstrate similar medical sequelae to clinically 'underweight' patients with AN and require hospitalizations at a comparable rate (Brennan et al, 2023;Garber et al, 2019;Sawyer et al, 2016;Whitelaw et al, 2018).…”