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]
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. 

Warren: With anxiety to the point where it’s part of a disorder — let’s say generalized anxiety disorder, mostly characterized by anxiety and worry about a whole bunch of different situations — we would treat it by teaching a patient about the role of worry in creating the symptoms and how to manage the worry. That sometimes involves challenging unrealistic thoughts or working to increase one’s ability to tolerate uncertainty, which is a big part of anxiety.
The cause of anxiety disorders is a combination of genetic and environmental factors.[47] Anxiety can stem itself from certain factors: genetics, medicinal side-effects, shortness of oxygen.[48] Risk factors include a history of child abuse, family history of mental disorders, and poverty. Anxiety disorders often occur with other mental disorders, particularly major depressive disorder, personality disorder, and substance use disorder.[49] To be diagnosed symptoms typically need to be present at least six months, be more than would be expected for the situation, and decrease functioning.[10][49] Other problems that may result in similar symptoms including hyperthyroidism, heart disease, caffeine, alcohol, or cannabis use, and withdrawal from certain drugs, among others.[49][7]
Panic disorder involves repeated episodes of sudden feelings of intense anxiety and fear or terror that reach a peak within minutes (panic attacks). You may have feelings of impending doom, shortness of breath, chest pain, or a rapid, fluttering or pounding heart (heart palpitations). These panic attacks may lead to worrying about them happening again or avoiding situations in which they've occurred.
Exercises to replace negative thoughts with positive ones: Make a list of the negative thoughts that might be cycling as a result of anxiety, and write down another list next to it containing positive, believable thoughts to replace them. Creating a mental image of successfully facing and conquering a specific fear can also provide benefits if anxiety symptoms relate to a specific cause, such as in a phobia.
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.
Social Anxiety Disorder;Fear of social situations in which the person is exposed to unfamiliar people or to possible scrutiny by others. The individual fears that he or she will act in a way (or show anxiety symptoms) that will be embarrassing and humiliating, often times leading to avoidance of social situations and severe distress when participation in social situations can't be avoided. [2]
We all experience anxiety. For example, speaking in front of a group can make us anxious, but that anxiety also motivates us to prepare and practice. Driving in heavy traffic is another common source of anxiety, but it helps keep us alert and cautious to avoid accidents. However, when feelings of intense fear and distress become overwhelming and prevent us from doing everyday activities, an anxiety disorder may be the cause.
2.This exposure happened either by directly experiencing the event(s), witnessing the event(s) in person, learning that the event(s) happened to a close friend or loved one (note: for cases of death or near death, it must have been violent or accidental), or being repeatedly exposed to the aversive details from traumatic events (e.g., as an emergency room doctor or nurse who frequently sees dead and mutilated bodies).
There are long-term, biological, environmental, and social causes of panic attacks. In 1993, Fava et al. proposed a staging method of understanding the origins of disorders. The first stage in developing a disorder involves predisposing factors, such as genetics, personality, and a lack of wellbeing.[11] Panic disorder often occurs in early adulthood, although it may appear at any age. It occurs more frequently in women and more often in people with above-average intelligence. Various twin studies where one identical twin has an anxiety disorder have reported a 31–88% incidence of the other twin also having an anxiety disorder diagnosis.[12]
Anxiety attacks symptoms and heart attack symptoms can seem similar because their signs and symptoms can be similar. But most medical professionals can quickly tell the difference as heart attacks have distinct symptoms that aren’t anxiety-like. If you are unsure of which is an anxiety attack symptom and which is a heart attack symptom, seek immediate medical advice. If the doctor diagnoses your symptoms as anxiety attack symptoms, you can feel confident the doctor’s diagnosis is correct. Therefore, there is no need to worry about a heart attack.

The electrocardiograph in a person with panic attacks often shows tachycardia, but does not usually show any of the changes typically seen in people with heart attacks or angina. However, if significant risk factors for cardiovascular disease are present, a noninvasive evaluation to rule out coronary artery disease (CAD) may sometimes be a good idea.

Given that anxiety attacks aren’t specifically outlined as a diagnosis in the DSM-5, the usage of the word is open to interpretation and different individuals may use it in varying ways and circumstances. For one person, an anxiety attack might be overthinking about a specific worry to the extent that they are unable to concentrate on anything else; for another, anxiety attack might refer to sweating and shortness of breath when faced with a certain situation.
Antidepressants are used to treat depression, but they can also be helpful for treating anxiety disorders. They may help improve the way your brain uses certain chemicals that control mood or stress. You may need to try several different antidepressant medicines before finding the one that improves your symptoms and has manageable side effects. A medication that has helped you or a close family member in the past will often be considered.