ReviewThe comorbidity of bipolar and anxiety disorders: prevalence, psychobiology, and treatment issues
Introduction
Symptoms of anxiety as well as sub-syndromal anxiety disorders often occur in patients with bipolar disorder. Indeed, Kraepelin (1921) was among the first to include anxiety as a symptom of mania. In categorizing mixed states of manic-depressive insanity, he described ‘depressive or anxious mania’ as ‘a morbid state…composed of flight of ideas, excitement, and anxiety…mood is anxiously despairing.’ He also described ‘excited depression,’ in which there was ‘great restlessness…mood is anxious, despondent, lachrymose, irritable, occasionally mixed with a certain self-irony.’ More recently, epidemiologic and clinical studies indicate that anxiety disorders are often comorbid with bipolar disorder. However, the importance of co-occurring anxiety symptoms and disorders as diagnostic and treatment issues in bipolar disorder has not received adequate study.
In this paper, we review epidemiological and clinical studies that have assessed the overlap of bipolar and anxiety disorders, with focus, on panic disorder and obsessive compulsive disorder, and to a lesser extent, social phobia and post-traumatic stress disorder. We address potential neural mechanisms to account for this co-occurrence, review relevant treatment response literature, and then discuss theoretical implications of a bipolar–anxiety disorder link. We conclude by presenting preliminary treatment guidelines for bipolar patients with various comorbid anxiety disorders.
Section snippets
Anxiety as a symptom of bipolar disorder
Although it is well established that symptoms of anxiety commonly occur in unipolar depression, the prevalence and clinical significance of anxiety symptoms in mania and bipolar depression have not been well studied (Strakowski et al., 1994, Young et al., 1993). However, when they have been specifically assessed, anxiety symptoms have been found to occur relatively frequently in both the manic and depressive phases of bipolar disorder. For example, in a recent study of 316 inpatients with
Psychobiological issues in the overlap of bipolar disorder and anxiety disorders
The psychobiology regarding the comorbidity of bipolar and anxiety disorders has not been well delineated. Most likely, a complicated interplay among various neurotransmitter systems and neuromodulator contributes to their overlap. However, the norepinephrine, dopamine, gamma-aminobutyric acid (GABA), and serotonin systems are presumably involved. Inositol, a simple isomer of glucose important in second messenger synthesis, might also play a role.
Discussion
It is imperative for clinicians to be aware of the striking comorbidity that exists between bipolar and anxiety disorders. Indeed, genetic data is now emerging to support already extensive epidemiological and clinical data suggesting that bipolar disorder and some anxiety disorders may be associated conditions. Biological mechanisms that may explain such associations are not well understood, but systems involving GABA, serotonin, norepinephrine, dopamine, and inositol may be involved. Treatment
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