Excerpt from Panic Disorder

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Background

Panic disorder is characterized by the spontaneous and unexpected occurrence of panic attacks, the frequency of which can vary from several attacks a day to only a few attacks a year.

To meet the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) criteria for panic disorder, panic attacks must be associated with more than 1 month of subsequent persistent worry about (1) having another attack, (2) consequences of the attack, or (3) significant behavioral changes related to the attack.

Panic attacks are a period of intense fear in which 4 of 13 defined symptoms develop abruptly and peak rapidly less than 10 minutes from symptom onset. To make the diagnosis of panic disorder, panic attacks cannot directly or physiologically result from substance use, medical conditions, or another psychiatric disorder.

The DSM-IV-TR delineates the following potential symptom manifestations of a panic attack:

• Palpitations, pounding heart, or accelerated heart rate
• Sweating
• Trembling or shaking
• Sense of shortness of breath or smothering
• Feeling of choking
• Chest pain or discomfort
• Nausea or abdominal distress
• Feeling dizzy, unsteady, lightheaded, or faint
• Derealization or depersonalization (feeling detached from oneself)
• Fear of losing control or going crazy
• Fear of dying
• Numbness or tingling sensations
• Chills or hot flashes

Panic disorder is usually qualified with the presence or absence of agoraphobia. Agoraphobia is defined as anxiety toward places or situations in which escape may be difficult or embarrassing. These anxiety-provoking situations are avoided or are endured with anxiety. (Note: Agoraphobia is not a stand-alone disorder; it is a descriptive term [eg, panic disorder with agoraphobia.])

Pathophysiology

Several non–mutually exclusive theories have been proposed to explain panic disorder, particularly from a biologic perspective, in response to the observed efficacy of certain pharmacologic agents for controlling the symptoms.

• The serotonergic model suggests an exaggerated postsynaptic receptor response to synaptic serotonin. Recent studies report subsensitivity of 5HT1A receptors. The 5HT system or one of its subsystems may play a role in the pathophysiology of panic disorder, the precise nature of which must be delineated by further investigation.
• The catecholamine model postulates increased sensitivity to adrenergic CNS discharges, with hypersensitivity of presynaptic alpha-2 receptors.
• Similarly, the locus ceruleus model explains that panic symptoms are due to increased local discharge resulting in adrenergic neuron stimulation, similar to the more general catecholamine theory. Locus ceruleus activity also affects the hypothalamic-pituitary-adrenal axis, which can respond abnormally to clonidine in patients with panic disorder.
• The lactate model focuses on symptom production by postulated aberrant metabolic activity induced by lactate.
• The false suffocation carbon dioxide hypothesis explains panic phenomena by hypersensitive brainstem receptors.
• The GABA model postulates decreased inhibitory receptor sensitivity, with a resultant excitatory effect.
• The neuroanatomic model suggests that panic attacks are mediated by a "fear network" in the brain that involves the amygdala, the hypothalamus, and the brainstem centers.
• The genetic hypothesis has attempted to refer panic disorder to definable genetic loci, without success to date.

Frequency

United States

Lifetime prevalence estimates range from 1.5-5% for panic disorder and 3-5.6% for panic attacks.

Mortality/Morbidity

Significant comorbidities are associated with panic disorder.

• Panic disorder often coexists with mood disorders, with mood symptoms potentially following the onset of panic attacks. Lifetime prevalence rates of major depression may be as much as 50-60%. These patients may be at higher risk of suicide attempts. Alcohol and other substance use disorders are also frequent sequelae of panic disorder.
• Medical conditions apparently share significant comorbidity with panic disorder. These conditions include cardiovascular disorders (eg, mitral valve prolapse, hypertension, cardiomyopathy) and other disorders (eg, chronic obstructive pulmonary disorder, irritable bowel syndrome, migraine headache).
• Aside from the significant psychological anguish of panic attacks, agoraphobia can result in numerous medical, social, and occupational consequences. These include increased health care use, social withdrawal and restricted role functioning, and decreased work productivity.

Race

Data on prevalence in different racial groups are inconsistent. Symptom manifestations may differ, with African Americans more often presenting with somatic symptoms and more likely seeking help in medical rather than psychiatric settings.

Sex

One-month prevalence estimates for women are 0.7% versus 0.3% for men (ie, women are more likely to be affected than men by a 2- to 3-fold factor).

Age

Panic disorder has a bimodal distribution, with highest incidence in late adolescence and a second peak in the mid 30s.

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