The symptoms of a<unk>  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 that translate this pH shift into autonomic and respiratory responses. Moreover, this hypocapnia and release of adrenaline during a<unk>  cause vasoconstriction resulting in slightly less blood flow to the head which causes dizziness and lightheadedness. A<unk>  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,<unk> rabrachial nucleus, and Locus coeruleus. In<unk> rticular, the amygdala has been suggested to have a critical role. The combination of increased activity in the amygdala (fear center) and brainstem along with decreased blood flow and blood sugar in the brain can lead to decreased activity in the prefrontal cortex (PFC) region of the brain. There is evidence that having an anxiety disorder increases the risk of cardiovascular disease (CVD). Those affected also have a reduction in heart rate variability. Cardiovascular disease People who have been diagnosed with<unk> nic disorder have approximately double the risk of coronary heart disease. Certain stress responses to depression also have been shown to increase the risk and those diagnosed with both depression and<unk> nic disorder are nearly three times more at risk.
Panic attack
Substance use disorder
Heat syncope
Dysautonomia
Shark attack
Hyperparathyroidism
Heat stroke
Hyperthyroidism