What immediate physical reaction is common in a panic disorder?

Chest pain or discomfort is a common immediate physical reaction in individuals experiencing a panic disorder. During a panic attack, the body enters a heightened state of arousal as part of the "fight or flight" response. This can lead to various symptoms such as increased heart rate, rapid breathing, and chest tightness or pain. These sensations can be very frightening, often leading individuals to fear they are having a heart attack or other serious medical condition. This fear can subsequently exacerbate the panic attack and contribute to the cycle of anxiety associated with the disorder.

The other options do not align with the immediate reactions typically associated with panic disorder. Persistent happiness is contrary to the experience of panic and anxiety. Muscle tension can occur but is not as immediate or defining as chest pain in the context of panic attacks. Memory loss is not a direct symptom of a panic attack, though individuals may feel confused or disoriented during an episode due to the overwhelming nature of their symptoms.