These episodes are a serious health problem in the U.S. At least 20% of adult Americans, or about 60 million people, will suffer from panic at some point in their lives. About 1.7% of adult Americans, or about 3 million people, will have full-blown panic disorder at some time in their lives, women twice as often as men. The most common age at which people have their first panic attack (onset) is between 15 and 19 years of age. Panic attacks are significantly different from other types of anxiety, in that panic attacks are very sudden and often unexpected, appear to be unprovoked, and are often disabling.
Panic attacks can occur unexpectedly during a calm state or in an anxious state. Although panic attacks are a defining characteristic of panic disorder, it is not uncommon for individuals to experience panic attacks in the context of other psychological disorders. For example, someone with social anxiety disorder might have a panic attack before giving a talk at a conference and someone with obsessive-compulsive disorder might have a panic attack when prevented from engaging in a ritual or compulsion.  
Anxiety disorders differ from normal feelings of nervousness or anxiousness and involve excessive fear or anxiety. Anxiety disorders are the most common of mental disorders and affect more than 25 million Americans. But anxiety disorders are treatable and a number of effective treatments are available. Treatment helps most people lead normal productive lives.
Some research suggests that people who have panic disorder might be very sensitive to sensory experiences (such as sunlight, smells and changes in the weather), but there's not enough evidence yet to say for sure. Also it's not clear whether having a high level of sensitivity to these sorts of things is something that might cause you to develop panic disorder, or whether it may be an effect of having it.
Moreover, this hypocapnia and release of adrenaline during a panic attack cause vasoconstriction resulting in slightly less blood flow to the head which causes dizziness and lightheadedness.[28][29] A panic attack can cause blood sugar to be drawn away from the brain and toward the major muscles. Neuroimaging suggests heightened activity in the amygdala, thalamus, hypothalamus, and brainstem regions including the periaqueductal gray, parabrachial nucleus, and Locus coeruleus.[30] In particular, the amygdala has been suggested to have a critical role.[31] The combination of high arousal in the amygdala and brainstem along with decreased blood flow and blood sugar in the brain can lead to dramatically decreased activity in the prefrontal cortex region of the brain.[32] There is evidence that having an anxiety disorder increases the risk of cardiovascular disease (CVD).[33] Those affected also have a reduction in heart rate variability.[33]
Carbonell says that understanding the physiology of fainting and reminding yourself of it is important. People faint when their blood pressure drops. A anxiety attack can make you feel like you’re going to faint, but you won’t because your blood pressure doesn't drop during an attack. Remind yourself out loud of truths like these to counter your fears.
Separation anxiety disorder: Separation anxiety is often thought of as something that only children deal with; however, adults can also be diagnosed with separation anxiety disorder. People who have separation anxiety disorder have fears about being parted from people to whom they are attached. They often worry that some sort of harm or something untoward will happen to their attachment figures while they are separated. This fear leads them to avoid being separated from their attachment figures and to avoid being alone. People with separation anxiety may have nightmares about being separated from attachment figures or experience physical symptoms when separation occurs or is anticipated.