While the worldwide prevalence of bipolar disorder is approximately 2%, it increases to 6% if the broad bipolar spectrum subtypes are also considered. Among other psychiatric conditions, anxiety disorders are most frequently observed in bipolar patients. Anxiety can be a symptom of bipolar disorder, and was first recognized by Kraepelin in 1921 who described “anxious mania” and also “excited depression”, which included a “great restlessness”. He specifically named anxiety as one of the components of this illness, but at present “anxiety” is not generally considered as a symptom of bipolar disorder, but rather as a comorbid condition. However, comorbid anxiety disorders have a significant impact on clinical presentation and prognosis of bipolar disorder in at least one-half of cases of bipolar disorder beyond the acute phase (in the euthymic phases). The aim of this study was to explore the correlation between anxiety and bipolar disorder through a critical review of the recent literature.
A search in MEDLINE and PUBMED was performed using the following keywords: bipolar disorder, anxiety disorders, bipolar spectrum subtypes and comorbidity. We selected both epidemiological and clinical studies written in English and published in international journals. Moreover, only publications with appropriate sample size, standardized experimental procedures and validated assessment scales were considered.
From a clinical point of view, the presence of comorbid anxiety in bipolar patients is related to more severe acute episodes (increased duration and severity), poorer course (rapid cycling) and increased risky behaviour such as substance abuse and suicide attempts. Moreover, bipolar patients with comorbid anxiety show a decreased response to pharmacological treatment and deterioration in both quality of life and social-work functioning.
There are two ways of looking at anxiety in bipolar disorders: as a symptom of the illness, or as a separate condition that requires a distinct treatment. Given the high rate of occurrence and significant clinical impact on quality of life of anxiety disorders in bipolar patients, we hypothesize that the anxiety symptoms are an integral part of clinical presentation: they do not identify a distinct disorder (comorbidity of bipolar disorder), and should therefore be considered an epiphenomenon of bipolar disorder itself.