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.
Repeated and persistent thoughts ("obsessions") that typically cause distress and that an individual attempts to alleviate by repeatedly performing specific actions ("compulsions"). Examples of common obsessions include: fear that failing to do things in a particular way will result in harm to self or others, extreme anxiety about being dirty or contaminated by germs, concern about forgetting to do something important that may result in bad outcomes, or obsessions around exactness or symmetry. Examples of common compulsions include: checking (e.g., that the door is locked or for an error), counting or ordering (e.g., money or household items), and performing a mental action (e.g., praying).

Anxiety is associated with abnormal patterns of activity in the brain. One way to treat anxiety is to directly target abnormal nerve cell activity. Neuromodulation or brain stimulation therapy is a non-invasive and painless therapy that stimulates the human brain. In some recent clinical trials, patients that did not respond to more traditional forms of treatment (i.e. medication) showed a reduction in symptoms of depression and anxiety. There are two main types of neuromodulation:

To the extent that a person is fearful of social encounters with unfamiliar others, some people may experience anxiety particularly during interactions with outgroup members, or people who share different group memberships (i.e., by race, ethnicity, class, gender, etc.). Depending on the nature of the antecedent relations, cognitions, and situational factors, intergroup contact may be stressful and lead to feelings of anxiety. This apprehension or fear of contact with outgroup members is often called interracial or intergroup anxiety.[34]
Panic attacks are often confusing for the sufferer. They are usually sudden and are accompanied by extremely intense physical sensations, leaving one to believe they may have a serious medical condition. Because the physical symptoms associated with a panic attack are similar to certain serious medical conditions, it is important to rule out any medical causes.
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.