Although recurring panic attacks are the central feature of Panic Disorder (PD), the presence of panic attacks does not necessarily indicate the diagnosis of PD, since they are a commonly associated feature of several other disorders. Therefore, it is necessary to differentiate between panic attacks warranting a diagnosis of PD and those that occur in the context of other disorders.
First, organic causes must be ruled out. Panic attacks can result from certain medical conditions (eg, hyperthyroidism, cardiac arrhythmias), the ingestion of various central nervous system stimulants (eg, cocaine, caffeine), or the withdrawal from central nervous system depressants (eg, alcohol, barbiturates). If the attacks only occur during the medical illness or substance use or withdrawal, PD is not diagnosed, as the attacks are judged to be a direct result of the illness or substance. Of course, after the onset of panic attacks, all patients should be evaluated to rule out the presence of medical factors.
Once organic causes are ruled out, PD must be differentiated from other psychiatric disorders that include panic attacks as an associated feature. A complicating factor is that panic attacks can occur in nearly all anxiety disorderpatients. Therefore, in order to determine the diagnostic significance of a panic attack, it is important to determine the focus of the panic and the context in which it occurs. As mentioned above, panic attacks that occur in the context of PD are not associated with a situational stimulus but instead appear to occur “out of the blue,” especially in the early stages of the disorder. In the DSM-IV, this type of attack is defined as an unexpected (uncued) panic attack. In contrast, panic attacks that almost always occur upon exposure to, or anticipation of, a specific stimulus are referred to as situationally bound (cued) panic attacks. Panic attacks that are likely to occur upon exposure to a specific stimulus, but are not invariably associated with that stimulus, are referred to as situationally predisposed panic attacks.
Both situationally bound and situationally predisposed panic attacks are associated with specific stimuli and are characteristic of other anxiety disorders. For example, if an individual experiences panic attacks only while giving a presentation during a business meeting, or experiences a panic attack one day prior to the meeting while anticipating his/her presentation, then this is more characteristic of social phobia, and would not warrant the diagnosis of PD.
Likewise, the obsessive-compulsive disorder patient with a contamination obsession will typically experience panic attacks when confronted with dirt or perceived germs; the specific phobia patient who fears dogs experiences a panic attack when confronted with a dog; and the posttraumatic stress disorder patient may experience a panic attack in a situation that resembles that in which the trauma occurred.
Although PD patients may experience situationally bound and situationally predisposed attacks following the development of agoraphobia (eg, a PD patient always experiences a panic attack when getting into an elevator), for the diagnosis of PD to be warranted, the initial attacks had to have been unexpected. Further complicating the differential diagnosis is the fact that one patient may have more than one disorder (ie, comorbidity), and therefore may experience each type of panic attack.