The comorbidity of bipolar and anxiety disorders: prevalence, psychobiology, and treatment issues

Abstract

Background: Although symptoms of anxiety as well as anxiety disorders commonly occur in patients with bipolar disorder, the pathophysiologic, theoretical, and clinical significance of their co-occurrence has not been well studied. Methods: The epidemiological and clinical studies that have assessed the overlap of bipolar and anxiety disorders are reviewed, with focus on panic disorder and obsessive–compulsive disorder (OCD), and to a lesser extent, social phobia and post-traumatic stress disorder. Potential neural mechanism and treatment response data are also reviewed. Results: A growing number of epidemiological studies have found that bipolar disorder significantly co-occurs with anxiety disorders at rates that are higher than those in the general population. Clinical studies have also demonstrated high comorbidity between bipolar disorder and panic disorder, OCD, social phobia, and post-traumatic stress disorder. Psychobiological mechanisms that may account for these high comorbidity rates likely involve a complicated interplay among various neurotransmitter systems, particularly norepinephrine, dopamine, gamma-aminobutyric acid (GABA), and serotonin. The second-messenger system constituent, inositol, may also be involved. Little controlled data are available regarding the treatment of bipolar disorder complicated by an anxiety disorder. However, adequate mood stabilization should be achieved before antidepressants are used to treat residual anxiety symptoms so as to minimize antidepressant-induced mania or cycling. Moreover, preliminary data suggesting that certain antimanic agents may have anxiolytic properties (e.g. valproate and possibly antipsychotics), and that some anxiolytics may not induce mania (e.g. gabapentin and benzodiazepines other than alprazolam) indicate that these agents may be particularly useful for anxious bipolar patients. Conclusions: Comorbid anxiety symptoms and disorders must be considered when diagnosing and treating patients with bipolar disorder. Conversely, patients presenting with anxiety disorders must be assessed for comorbid mood disorders, including bipolar disorder. Pathophysiological, theoretical, and clinical implications of the overlap of bipolar and anxiety disorders are discussed.