The 2 most common anxiety disorders are generalized anxiety disorder (GAD) and panic disorder. Approximately 5.7% of people in community samples will meet diagnostic criteria for GAD in their lifetime; the rate is about 4.7% for panic disorder (with or without agoraphobia).1 GAD—which is characterized by excessive and uncontrollable worry about a variety of topics (along with associated features such as trouble sleeping and impaired concentration)—is often chronic and is associated with significant costs to the individual and to society.2,3
Panic disorder—characterized by recurrent, unexpected panic attacks—can be similarly intractable (particularly when is it accompanied by agoraphobia) and costly.4,5 Panic attacks are discrete periods of intense fear or discomfort that manifest with sweating, trembling, accelerated heart rate, and concern about having another panic attack. Many people experience panic attacks without meeting full diagnostic criteria for panic disorder (about 28.3% lifetime prevalence).6 Furthermore, panic attacks have been identified as a risk factor for various other forms of psychopathology, including GAD.7
Given the widespread occurrence of GAD, panic disorder, and panic attacks, it is not surprising that these conditions are frequently comorbid. An international study of lifetime comorbidities found a high rate (21.8%) of panic disorder and GAD; most people (55.8%) reported that the symptoms of GAD and panic disorder began within 1 year of each other.8 Unfortunately, while effective treatment strategies are available for both panic disorder and GAD, little is known about how to best treat these disorders when they are comorbid.
Diagnostic issues
The first task to effectively address comorbid GAD and panic disorder is to make the appropriate diagnosis. A variety of general medical conditions that mimic features of panic 
In GAD, somatic symptoms such as muscle tension or feeling “keyed up” or “on edge” may occur, but they present differently than those that arise during a panic attack. Panic attack–related somatic symptoms tend to develop abruptly, then peak and subside relatively quickly, whereas GAD-related somatic symptoms tend to come on more gradually, and are present at a lower level for longer periods. GAD-related somatic symptoms may be experienced as aversive by the individual but generally are not catastrophically misinterpreted (eg, “I am dying”).
In addition to the symptom overlap between GAD and panic attacks, there is overlap between GAD and panic disorder; worry is a component of both disorders. Panic disorder is associated with recurrent panic attacks and worries about future attacks and their consequences or meaning.
