Some of these symptoms will most likely be present in a panic attack. The attacks can be so disabling that the person is unable to express to others what is happening to them. A doctor might also note various signs of panic: The person may appear to be very afraid or shaky or be hyperventilating (deep, rapid breathing that causes dizziness). Anxiety attacks that take place while sleeping, also called nocturnal panic attacks, occur less often than do panic attacks during the daytime, but affect a large percentage of people who suffer from daytime panic attacks. Individuals with nocturnal panic attacks tend to have more respiratory symptoms associated with panic and have more symptoms of depression and of other psychiatric disorders compared to people who do not have panic attacks at night. Nocturnal panic attacks tend to result in sufferers waking suddenly from sleep in a state of sudden fright or dread for no known reason. As opposed to people with sleep apnea and other sleep disorders, sufferers of nocturnal panic can have all the other symptoms of a panic attack. Although nocturnal panic attacks usually last no more than 10 minutes, it can take much longer for the person to fully recover from the episode.
“Anxiety attack” is not a formal, clinical term, but one that is used by many people to describe all sorts of things, from feeling worried about an upcoming event to intense feelings of terror or fear that would meet the diagnostic criteria for a panic attack. In order to understand what someone means by “anxiety attack,” it is necessary to consider the context in which the symptoms occur.
Agoraphobia is often comorbid with panic disorder — meaning people often suffer from both conditions at the same time. It's an intense fear of not being able to escape whatever place you're in, and can often lead to an avoidance of leaving the house. People with agoraphobia can fear situations where this anxiety might flare up, and typically don't feel comfortable or safe in public, crowded places. 
Anxiety attacks can last anywhere between a few moments to 30 or more minutes. It’s also common for subsequent anxiety attacks to follow, causing the overall anxiety attack experience to last much longer as one episode is followed by another. Even though anxiety attacks eventually end, it’s common for the symptoms and after effects of an anxiety attack to linger for hours or even days, depending upon the severity of the attack and the level of stress your body is under.
People with panic disorder often worry about when the next attack will happen and actively try to prevent future attacks by avoiding places, situations, or behaviors they associate with panic attacks. Worry about panic attacks, and the effort spent trying to avoid attacks, cause significant problems in various areas of the person’s life, including the development of agoraphobia (see below).
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