Understanding the neurobiology of comorbidity in anxiety disorders.

Anxiety and depression are common disorders that frequently co-exist. Both disorders show good response to antidepressants, especially the selective serotonin reuptake inhibitors. Some suggest that these disorders are variants of the same underlying brain pathology. This review examines the similarities and differences between anxiety and depression in terms of the known neurobiological etiologic mechanisms as well as their biological underpinnings and response to treatment. Sufficient and significant differences between these disorders support the view that they are independent entities. Shared abnormalities in the 5HT1A receptor function, for example, may help explain some of the comorbidity.