Get a clear understanding of panic disorder, the neurobiology of panic disorder and medication treatments for panic disorder.

Panic Disorder is an anxiety disorder characterized by recurrent unexpected panic attacks, with at least one of the attacks being followed by one or more of the following symptoms: (a) persistent concern about having additional attacks; (b) worry about the implication of the attack or its consequences; (c) a significant change in behavior related to the attacks for example, avoiding places where one has experienced an attack previously. A high percentage of patients with Panic Disorder also suffer from depression, 80.2% are reported as suffering from depression over a 12 month period and 55.6% are reported as suffering over a lifetime. Onset of, and recovery from, Panic Disorder varies among patients, but those who panic disorder also suffer from depression tend to have chronic Panic Disorder and a high rate of relapse. Furthermore, having both illnesses significantly contributes to psychological distress, interpersonal impairment, and overall impairment. The substantial cost to society as a result of untreated Panic Disorder may be ameliorated with more widespread awareness, recognition, and appropriate early treatment.

Neurobiology of Panic Disorder

Evidence suggests that certain neurochemical receptors (serotonin receptors and benzodiazipine/GABA receptors) function abnormally in the brains of patients with Panic Disorder. This evidence is supported by the fact that Serotonin Reuptake Inhibitors (SSRIs) have been shown to be effective in the treatment of patients with anxiety disorders, including Panic Disorder. Evidence arguing for a role of benzodiazepine receptor dysfunction in anxiety disorders comes predominantly from studies showing that drugs which stimulate benzodiazepine activity in the brain have an anti-anxiety effect while those that repress that activity have an anxiety causing effect.

Current brain imaging studies in the Mood and Anxiety Disorders Program at the National Institute of Mental Health will advance our knowledge regarding the neurobiology of Panic Disorder by employing Positron Emission Tomography (PET) scans which can track slightly radioactive substances. These substances bind to the receptors in question, allowing scientists to compare benzodiazepine receptor and serotonin receptor function in patients with Panic Disorder. This may ultimately lead to the development of novel compounds for the treatment of patients with anxiety disorders, particularly Panic Disorder.

Pharmacological Treatment Options for Panic Disorder:

The main goal of treatment in patients with Panic Disorder is to effect a rapid reduction in symptom severity and improve functioning. Generally, patients with Panic Disorder respond very well to pharmacotherapy, and response rates are even better when medication is combined with psychotherapy. Antidepressants and benzodiazepines are mainstays in the pharmacological treatment of patients with Panic Disorder. Among the antidepressants, both tricyclic antidepressants and SSRIs are effective in the treatment of Panic Disorder. While tricyclic antidepressants are effective, their unfavorable side effects can make them unpleasant to take, and limits their widespread clinical use. Other antidepressants, such as SSRIs, have not only been shown to be effective, but to have a better side effect profile compared to the tricyclic antidepressants. Although SSRIs have proven efficacy in the treatment of Panic Disorder there is delay of up to 4 weeks before the full effects of the medications are experienced.

Combining SSRIs with benzodiazepines during the course of anti-panic treatment appears to be a natural psychopharmacologic approach. This strategy was designed to take advantage of the rapid anti-anxiety effects of benzodiazepines prior to the delayed onset of SSRI treatment thereby accelerating and possibly enhancing overall treatment effects. However, there are only a very small number of placebo controlled treatment studies supporting such an approach in Panic Disorder, and the effectiveness of this treatment approach remains to be demonstrated in patients with Panic Disorder and concurrent depressive symptoms.

Given the abundance of antidepressants, how does the clinician rationally choose a treatment option? Although most patients will eventually respond to a treatment, there are no predictors for the initial selection of a medication. Initial treatment is usually chosen based upon the evidence that the compound is effective, has a favorable side-effect profile, is cost effective, and is convenient to take. Medications used to treat Panic Disorder should be chosen on the basis of a thorough medical and psychiatric evaluation. It is also important that the patient fully complies with treatment since poor adherence to therapy may account for as much as 20% of treatment resistant cases.

Thanks to our understanding of the pathophysiology of Panic Disorder additional treatment strategies are being investigated. These studies and studies of the underlying biology of Panic Disorder will lead to the development of new treatments to add to the current arsenal.

About the author: Alexander Neumeister, M.D. is an Associate Professor of Psychiatry at Yale University School of Medicine and Director, Molecular Imaging Program of the Clinical Neuroscience Division. He is affiliated with the Mood and Anxiety Disorders Research Program at the National Institute of Mental Health.

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