Which comes first? New insights on comorbidity between eating disorders and bipolar disorders

Abstract

Aims

Bipolar disorders (BDs) and eating disorders (EDs) are both common and severe mental illness and present wide areas of symptomatological overlap. The present study aims to focus on the most significant aspects of this comorbidity.

Methods

This review summarizes epidemiology, aethiopathology, prognostic impact, assessment, treatment of comorbidity between BDs and EDs, and comorbidity between bipolar or eating disorders and other psychiatric disorders. We have reviewed articles published in PubMed/Medline, Scopus, Embase, ScienceDirect from 2005 to 2020 concerning comorbidity between eating and bipolar disorders, and systematic reviews or metanalysis on comorbidities between EDs or BDs and other psychiatric disorders.

Results

Studies that specifically evaluate the prevalence of EDs in patients with bipolar disorder are more than the studies that investigate the opposite. In BDs, binge eating disorder (BED) represents the most common eating disorder with a prevalence ranging from 8,8% to 28,8%, whereas BN has a prevalence ranging from 4,8% to 10%, and AN from 1% to 7,4%. Instead, in ED patients, prevalence of bipolar disorders ranges from 11,5% to 68.1%.

The relationship between EDs and BDs has not been yet investigated enough and consequently has not been totally understood. The presence of EDs has been considered as a marker of clinical severity in patients with bipolar disorders, whereas the presence of bipolar disorder in patients with EDs seems not to have a considerable effect on the age at onset of ED symptoms and on their severity. Comorbidities between EDs or BDs and other psychiatric disorders were also examined.

Discussion

Given the strong co-occurrence of eating and bipolar disorder, the treatment for one of these should consider that the other one may co-exist, and therefore should focus on both of them. In patients suffering from one of these disorders, the early screening for the other one should be made. As for pharmacological treatment, it is mandatory to consider that pharmacological treatment effective for one of the two disorders could worsen symptoms of the other, for instance many psychotropic medications could cause weight gain. Further studies are needed to reach an early diagnosis through the development of screening tools, and to deepen aspects of this comorbidity that remain still unknown with particular regard to pharmacological treatment and to biopsychological aspects that might be useful in determining the aetiopathology.