Clinical phenotype and genetic risk factors for bipolar disorder with binge eating: an update

ABSTRACT

Introduction: Clinical and genetic study of psychiatric conditions has underscored the co-occurrence of complex phenotypes and the need to refine them. Bipolar Disorder (BD) and Binge Eating (BE) behavior are common psychiatric conditions that have high heritability and high co-occurrence, such that at least one quarter of BD patients have BE (BD + BE). Genetic studies of BD alone and of BE alone suggest complex polygenic risk models, with many genetic risk loci yet to be identified.

Areas covered: We review studies of the epidemiology of BD+BE, its clinical features (cognitive traits, psychiatric comorbidity, and role of obesity), genomic studies (of BD, eating disorders (ED) defined by BE, and BD + BE), and therapeutic implications of BD + BE.

Expert opinion: Subphenotyping of complex psychiatric disorders reduces heterogeneity and increases statistical power and effect size; thus, it enhances our capacity to find missing genetic (and other) risk factors. BD + BE has a severe clinical picture and genetic studies suggests a distinct genetic architecture. Differential therapeutic interventions may be needed for patients with BD + BE compared with BD patients without BE. Recognizing the BD + BE subphenotype is an example of moving towards more precise clinical and genetic entities.

KEYWORDS:

• Bipolar
• binge eating
• genetics
• GWAS
• eating disorders

Article highlights

• BD and BE commonly co-occur, with significant clinical implications. These patients are more likely to be female and to have higher levels of ED psychopathology, suicidality, mood instability, and anxiety disorder comorbidity, and significantly higher mean BMI.

• BD and BE have high heritability rates and are likely polygenic, with multiple genetic variants conferring small effects of risk.

• BD + BE as a subphenotype is an example of investigating disease subtypes with potentially distinct genetic architectures.

• Considering subphenotypes, in spite of impacting sample sizes, reduce heterogeneity and potentially increase statistical power and effect sizes in genetic studies.

• BD + BE may have a distinct genetic architecture from BD without BE. Top associations have been found with genetic variants of PRR5-ARHGAP8, but these findings are highly preliminary and in need of replication. Pathway-level analyses suggest associations with the Wnt canonical pathway.

• Genetic information regarding BD + BE is far too preliminary to inform treatment of this subphenotype, but suggests it may require differential treatment as compared to BD without BE.

Declaration of interest

M Frye has been a consultant to Actify Neurotherapies, Allergan, Intra-Cellular Therapies, Inc., Janssen, Myriad, Neuralstem Inc.,Takeda, Teva Pharmaceuticals. He has been the principal or co-investigator on studies sponsored by Assurex Health, Mayo Foundation, and Medibio. He has received continual medical education and travel related honoraria from the American Physician Institute, CME Outfitters, Global Academy for Medical Education. Mayo Clinic has a financial interest in AssureRX and OneOme and the technology referenced in this publication/presentation. SL McElroy has been a consultant to or member of the scientific advisory boards of Allergan, Avanir, Bracket, F. Hoffmann-La Roche Ltd., Mitsubishi Tanabe Pharma America, Myriad, Opiant, Shire, and Sunovion. She has been a principal or co-investigator on studies sponsored by Allergan, Avanir, Azevan, Brainsway, Marriott Foundation, Medibio, Myriad, Neurocrine, Novo Nordisk, Shire, and Sunovion. She is also an inventor on United States Patent No. 6,323,236 B2, Use of Sulfamate Derivatives for Treating Impulse-Control Disorders, and along with the patent’s assignee, University of Cincinnati, Cincinnati, Ohio, has received payments from Johnson & Johnson, which has exclusive rights under the patent. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or conflict with the subject matter or materials discussed in this manuscript apart from those disclosed.

Reviewer disclosures

A reviewer on this manuscript has been the speaker for and advisory board member of Bristol-Myers Squibb, Janssen-Cilag, Astra-Zeneca, Rovi, Lundbeck, Otsuka, GSK and Pfizer. Peer reviewers on this manuscript have no other relevant financial relationships or otherwise to disclose.

Additional information

Funding

This paper was funded by the Marriot Foundation, the Mayo Clinic Center for Individualized Medicine, and the Lindner Center of HOPE.