Cognitive performance and weight gain in patients with severe anorexia nervosa

Simone Daugaard Hemmingsen*

*Corresponding author for this work

Research output: ThesisPh.D. thesis

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Abstract

Introduction: Anorexia nervosa is characterized by fear of weight gain, a distorted body perception, and restricted food intake leading to low body weight. There is no consensus on the definition of severe anorexia nervosa. The Diagnostic and Statistical Manual of Mental Disorders 5th edition presents categories of severe anorexia nervosa (body mass index 15-15.99 kg/m2 ) and extreme anorexia nervosa (body mass index <15 kg/m2 ). Severe underweight may affect cognitive functioning and mental health in patients with anorexia nervosa. However, studies investigating whether cognitive functioning is retained or can be regained in patients with severe and extreme anorexia nervosa are needed. A deeper understanding of the cognitive mechanisms involved in severe and extreme anorexia nervosa could provide the basis for highly warranted adaptation and development of treatments for these patients. 

Objectives: The PhD thesis includes four studies (five papers) and addresses the following objectives:
Study 1: Investigate whether cognitive performance improves following weight gain in patients with anorexia nervosa
Study 2: Determine whether patients with severe and extreme anorexia nervosa have cognitive flexibility difficulties
Study 3: Investigate changes in cortisol, depression, and anxiety levels during hospitalization in patients with severe and extreme anorexia nervosa
Study 4: Examine cognitive performance in patients with severe and extreme anorexia nervosa, and whether weight gain during hospitalization is associated with improved cognitive performance.

Methods: Study 1 (Paper 1) was a systematic review of cognitive performance and weight gain in patients with anorexia nervosa. Study 2 (Paper 2) used a cross-sectional design to investigate cognitive flexibility in patients with severe and extreme anorexia nervosa compared to healthy control participants. Study 3 (Paper 3) was a longitudinal study that investigated cortisol concentrations and depression and anxiety symptoms in patients with severe and extreme anorexia nervosa. Study 4 (Paper 4) examined memory, cognitive flexibility, attention, and processing speed in patients with severe and extreme anorexia nervosa in a longitudinal design. A case report was conducted after the inclusion of an extreme case in Study 4 (Paper 5).

The three clinical studies included patients hospitalized in the specialized Nutrition Unit at the Department of Endocrinology at Odense University Hospital in Denmark. They were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders 5th edition. Study 1: The systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. It was registered at PROSPERO (ID CRD42019081993) prior to the literature searches in the databases PubMed, PsychInfo, EMBASE, and Cochrane Library.

Study 2: Cognitive flexibility was assessed in patients with severe and extreme anorexia nervosa and healthy control participants using the Wisconsin Card Sorting Test.

Study 3: Plasma and 24-hour urine cortisol concentrations and self-reported depression, anxiety, and stress symptoms were measured in patients at hospital admission and at discharge.

Study 4: Cognitive performance was investigated with the Wechsler Memory Scale III, the d2 Test of Attention, The Wechsler Adult Intelligence Scale IV (Processing Speed Index), and the Delis Kaplan Executive Function System (Verbal Fluency, Design Fluency, and Trail Making) in patients at hospital admission, at discharge, and at follow-up.

Results: The systematic review (Study 1, Paper 1) included 24 research papers that investigated cognitive performance in patients with anorexia nervosa before and after weight gain. The literature was limited, and the studies used a variety of tests. For the studies that investigated adults, few used similar cognitive tests and they found mixed results. In children and adolescents, processing speed seemed to improve after weight gain contrary to cognitive flexibility. 

In Study 2 (Paper 2), the 34 patients included had lower cognitive flexibility than the 34 healthy control participants after controlling for age and years of education. We found no significant associations between cognitive flexibility and body mass index, illness duration, depression, or eating disorder symptoms among patients with severe and extreme anorexia nervosa.

Out of 36 patients investigated at admission, 27 patients completed measurements at discharge in Study 3 (Paper 3). We found no statistically significant changes in cortisol, depression, and anxiety levels during hospitalization in the patients with severe and extreme anorexia nervosa. Nor did we find any associations between cortisol and psychopathology. 

In Study 4 (Paper 4), we found that the 33 patients included had normal cognitive performance. Of these, 22 patients completed discharge assessments and 18 completed follow-up assessments a few months after discharge. Between admission and discharge, the patients gained a mean of 11.3% body weight and significantly improved memory, processing speed, and concentration performance. However, we found no statistically significant associations between the cognitive improvement and percentage weight gain. Between discharge and follow-up, we found no improvement in performance.

The case report (Paper 5) described a 35-year-old woman with a body mass index of 7.7 who performed normal on cognitive measurements, except cognitive flexibility assessed with the Wisconsin Card Sorting Test.

Conclusion: Based on the studies in this PhD thesis, neuropsychological assessment of severely malnourished patients with anorexia nervosa is possible. Patients with severe and extreme anorexia nervosa seemed to have normal cognitive performance, despite being severely underweight and depressed, but seemed to display cognitive inflexibility compared to healthy control individuals. A theory of cognitive adaptation to severe malnutrition in patients with anorexia nervosa was introduced. It was recommended to evaluate individually whether a patient with severe or extreme anorexia nervosa has specific cognitive difficulties that may be assessed and addressed in treatment. In addition, it was suggested that future studies of cognitive performance should distinguish between children, adolescents, and adults. Future research on larger samples could compare patients with anorexia nervosa with very low body mass indexes to patients with higher body mass indexes, in order to investigate whether weight status in adults with anorexia nervosa is associated with cognitive performance.
Original languageEnglish
Awarding Institution
  • University of Southern Denmark
Supervisors/Advisors
  • Støving, René Klinkby, Principal supervisor
  • Lichtenstein, Mia Beck, Co-supervisor
  • Sjögren, Jan Magnus, Co-supervisor, External person
Date of defence5. Oct 2023
Publisher
DOIs
Publication statusPublished - 19. Jun 2023

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