Hippocampal volume, function, and related molecular activity in anorexia nervosa: A scoping review

ABSTRACT

Introduction

Anorexia nervosa (AN) is a serious and persistent eating disorder, characterized by severe dietary restriction and weight loss, with a third of patients developing a  severe-enduring form. The factors contributing to this progression are poorly understood, although there is evidence for impairments in neural structures such as the hippocampus, an area particularly affected by malnutrition and chronic stress.

Areas covered

This study aimed to map the evidence for alterations in hippocampal volume, function, and related molecular activity in anorexia nervosa. PubMed, PsycINFO, and Web of Science were searched for studies related to hippocampal function and integrity using a range of methodologies, such as neuropsychological paradigms, structural and functional magnetic resonance imaging, and analysis of blood components.

Expert opinion

Thirty-nine studies were included in this review. The majority were neuroimaging studies, which found hippocampus-specific volumetric and functional impairments. Neuropsychological studies showed evidence for a specific memory and learning impairments. There was some evidence for molecular abnormalities (e.g. cortisol), although these were few studies. Taken together, our review suggests that the hippocampus might be a particular region of interest when considering neurobiological approaches to understanding AN. These findings warrant further investigation and may lead to novel treatment approaches.

KEYWORDS:

• Anorexia nervosa
• hippocampus
• hippocampal function
• scoping review

Article highlights

• Anorexia nervosa (AN) is a psychiatric disorder with a protracted course and a high mortality rate.

• The factors contributing to the severe-enduring state are unclear, although there is evidence for global and localized brain shrinkage in the active stages of the illness.

• The hippocampus appears to show a marked volume reduction in active AN, which is reversible with weight restoration.

• There are alterations in neuropsychological performance and molecular factors that may be associated with the reduced integrity of the hippocampus in AN.

• A minority of studies investigated specific neuropsychological and molecular markers of hippocampal function.

• There is a need for more research on the hippocampus in AN, to provide direction for future treatments and theoretical models encompassing the hippocampus.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with \the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants, or patents received or pending, or royalties.

Reviewer declaration

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

J. Keeler acknowledges salary support from a Medical Research Council (MRC) funded Doctoral Training Partnership stipend (ref: MR/N013700/1). S. Thuret acknowledges financial support from the Medical Research Council. H. Himmerich, J. Treasure, and O. Patsalos acknowledge salary support from the National Institute for Health Research (NIHR) Maudsley Biomedical Research Centre (BRC) for Mental Health.