Great questions. Unfortunately, there is usually no clear cut answer – and like many mental health disorders – it is likely caused by a combination of genetic, behavioral, and developmental factors. Anatomically speaking, Generalized Anxiety Disorder is most closely related to a disruption in the functional connectivity of the amygdala – the “emotional control center” of the brain – and how it processes feelings of fear and anxiety. Genetics also play a role in Generalized Anxiety Disorder. If you have a family member that also suffers from this disorder, your chances of suffering from it are increased, especially in the presence of a life stressor. Interestingly, long-term substance abuse also increases your chances of Generalized Anxiety Disorder, as the use of benzodiazepines can worsen your anxiety levels, as can excessive alcohol use. Tobacco use and caffeine are also both associated with increased levels of anxiety.
Although many people breathe into a paper bag in an attempt to alleviate the hyperventilation that can be associated with panic, the benefit received may be the result of the individual thinking it will help (a placebo effect). Unfortunately, breathing into a paper bag while having trouble breathing can worsen symptoms when the hyperventilation is caused by a condition associated with oxygen deprivation, like an asthma attack or a heart attack.

Poverty and low education level tend to be associated with anxiety, but it is unclear if those factors cause or are caused by anxiety. While some statistics suggest that disadvantaged ethnic minorities tend to suffer from internalizing disorders like panic disorder less often than the majority population in the United States, other research shows that may be the result of differences in how ethnic groups interpret and discuss signs and symptoms of intense fright, like panic attacks. Also, panic and other anxiety disorders are thought to persist more for some ethnic minorities in the United States. Difficulties the examiner may have in appropriately recognizing and understanding ethnic differences in symptom expression is also thought to play a role in ethnic differences in the reported frequency of panic and other internalizing disorders.

Persistent and excessive fear of a specific object or situation, such as flying, heights, animals, toilets, or seeing blood. Fear is cued by the presence or anticipation of the object/situation and exposure to the phobic stimulus results in an immediate fear response or panic attack. The fear is disproportionate to the actual danger posed by the object or situation. Commonly, adults with specific phobias will recognize that their fear is excessive or unreasonable.
Many neurotransmitters are affected when the body is under the increased stress and anxiety that accompany a panic attack. Some include serotonin, GABA (gamma-aminobutyric acid), dopamine, norepinephrine and glutamate. More research into how these neurotransmitters interact with one another during a panic attack is needed to make any solid conclusions, however.
The prognosis for people who suffer a panic attack is overall, good. Some people have a single attack and are never bothered again. Yet, two-thirds of people experiencing a panic attack go on to be diagnosed with panic disorder. Also, half of those who go through a panic attack might develop clinical depression within the following year, if not treated promptly. Occasionally, a person will, after a long evaluation, be diagnosed with a medical condition that causes panic symptoms.

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.