For example, once you notice you are scaring yourself with anxious thinking, you can change your thinking to calming thoughts, which will stop stress responses and their physiological, psychological, and emotional effects. As you calm yourself down, your body will follow by stopping the flow of stress hormones. As stress hormones are used up or expelled, the sensations, symptoms, and feelings of panic will subside…in time.
The symptoms of a panic attack may cause the person to feel that their body is failing. The symptoms can be understood as follows. First, there is frequently the sudden onset of fear with little provoking stimulus. This leads to a release of adrenaline (epinephrine) which brings about the fight-or-flight response when the body prepares for strenuous physical activity. This leads to an increased heart rate (tachycardia), rapid breathing (hyperventilation) which may be perceived as shortness of breath (dyspnea), and sweating. Because strenuous activity rarely ensues, the hyperventilation leads to a drop in carbon dioxide levels in the lungs and then in the blood. This leads to shifts in blood pH (respiratory alkalosis or hypocapnia), causing compensatory metabolic acidosis activating chemosensing mechanisms which translate this pH shift into autonomic and respiratory responses.[25][26] The person him/herself may overlook the hyperventilation, having become preoccupied with the associated somatic symptoms.[27]
People with panic attacks often report a fear of dying or heart attack, flashing vision, faintness or nausea, numbness throughout the body, heavy breathing and hyperventilation, or loss of body control. Some people also suffer from tunnel vision, mostly due to blood flow leaving the head to more critical parts of the body in defense. These feelings may provoke a strong urge to escape or flee the place where the attack began (a consequence of the "fight-or-flight response", in which the hormone causing this response is released in significant amounts). This response floods the body with hormones, particularly epinephrine (adrenaline), which aid it in defending against harm.[9]
Post-traumatic stress disorder -- or PTSD -- was considered to be a type of anxiety disorder in earlier versions of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders. But in 2013, PTSD was reclassified as its own condition. It describes a range of emotional reactions caused by exposure to either death or near-death circumstances (such as fires, floods, earthquakes, shootings, assault, automobile accidents, or wars) or to events that threaten one's own or another person's physical well-being. The traumatic event is re-experienced with fear of feelings of helplessness or horror and may appear in thoughts and dreams. Common behaviors include the following:
Anxiety is an emotion characterized by an unpleasant state of inner turmoil, often accompanied by nervous behaviour such as pacing back and forth, somatic complaints, and rumination.[1] It is the subjectively unpleasant feelings of dread over anticipated events, such as the feeling of imminent death.[2][need quotation to verify] Anxiety is not the same as fear, which is a response to a real or perceived immediate threat,[3] whereas anxiety involves the expectation of future threat.[3] Anxiety is a feeling of uneasiness and worry, usually generalized and unfocused as an overreaction to a situation that is only subjectively seen as menacing.[4] It is often accompanied by muscular tension,[3] restlessness, fatigue and problems in concentration. Anxiety can be appropriate, but when experienced regularly the individual may suffer from an anxiety disorder.[3]
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]

To receive a diagnosis of panic disorder, the panic attacks must be unexpected and during the attack four or more of the above symptoms must occur. For panic attacks that are expected, meaning they might not be expected by the individual but are expected in relation to any phobia, anxiety or other mental health disorder, four or more symptoms must also occur.

Panic attacks involve sudden feelings of terror that strike without warning. These episodes can occur at any time, even during sleep. People experiencing a panic attack may believe they are having a heart attack or they are dying or going crazy. The fear and terror that a person experiences during a panic attack are not in proportion to the true situation and may be unrelated to what is happening around them. Most people with panic attacks experience several of the following symptoms:
As is the case the more generalized forms of social anxiety, intergroup anxiety has behavioral, cognitive, and affective effects. For instance, increases in schematic processing and simplified information processing can occur when anxiety is high. Indeed, such is consistent with related work on attentional bias in implicit memory.[35][36][37] Additionally recent research has found that implicit racial evaluations (i.e. automatic prejudiced attitudes) can be amplified during intergroup interaction.[38] Negative experiences have been illustrated in producing not only negative expectations, but also avoidant, or antagonistic, behavior such as hostility.[39] Furthermore, when compared to anxiety levels and cognitive effort (e.g., impression management and self-presentation) in intragroup contexts, levels and depletion of resources may be exacerbated in the intergroup situation.
The emotional effects of anxiety may include "feelings of apprehension or dread, trouble concentrating, feeling tense or jumpy, anticipating the worst, irritability, restlessness, watching (and waiting) for signs (and occurrences) of danger, and, feeling like your mind's gone blank"[20] as well as "nightmares/bad dreams, obsessions about sensations, déjà vu, a trapped-in-your-mind feeling, and feeling like everything is scary."[21]
About 12% of people are affected by an anxiety disorder in a given year and between 5-30% are affected at some point in their life.[49][50] They occur about twice as often in women than they do in men, and generally begin before the age of 25.[10][49] The most common are specific phobia which affects nearly 12% and social anxiety disorder which affects 10% at some point in their life. They affect those between the ages of 15 and 35 the most and become less common after the age of 55. Rates appear to be higher in the United States and Europe.[49]

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.  

It is common for a person with one anxiety disorder to also have another anxiety disorder. Anxiety disorders are also frequently accompanied by depression or substance abuse. Anxiety disorders can coexist with physical health conditions as well. In such instances, these physical health conditions will also need to be treated. Before undergoing any treatment, it is important to have a thorough medical exam to rule out other possible causes.
Anxiety disorders are treated through medication and therapy. You might feel embarrassed talking about the things you are feeling and thinking, but talking about it, say experts, is the best treatment. A particular form of therapy is considered most effective: cognitive behavioral therapy, or CBT for short. Antidepressants — the types of medication most frequently used to treat depression — are the drugs that also work best for anxiety disorders.
The degree of accompanying stress response and its physiological, psychological, and emotional changes are directly proportional to the degree of anxiety. For example, if you are only slightly concerned, such as being slightly nervous about meeting someone new, the body produces a small degree stress response. The small degree stress response can be so slight that you don’t even notice it.
Selective mutism: A somewhat rare disorder associated with anxiety is selective mutism. Selective mutism occurs when people fail to speak in specific social situations despite having normal language skills. Selective mutism usually occurs before the age of 5 and is often associated with extreme shyness, fear of social embarrassment, compulsive traits, withdrawal, clinging behavior, and temper tantrums. People diagnosed with selective mutism are often also diagnosed with other anxiety disorders.