Social anxiety disorder, also known as social phobia, is a diagnosis within psychiatry and other mental health professions referring to excessive long-lasting social anxiety causing relatively extreme distress and impaired ability to function in at least some areas of daily life. The diagnosis can be of a 'specific' disorder (when only some particular situations are feared) or a generalized disorder.

Generalized social anxiety disorder typically involves a persistent, intense, and chronic fear of being judged by others and of potentially being embarrassed or humiliated by their own actions. These fears can be triggered by perceived or actual scrutiny by others. While the fear of social interaction may be recognized by the person as excessive or unreasonable, considerable difficulty can be encountered overcoming it.

Physical symptoms often accompanying social anxiety disorder include excessive blushing, sweating (hyperhidrosis), trembling, nausea, and stammering. Panic attacks may also occur under intense fear and discomfort. Some sufferers may use alcohol or other drugs to reduce fears and inhibitions at social events.

According to the Diagnostic and Statistical Manual of Mental Disorders, social anxiety disorder is a persistent fear of one or more situations in which the person is exposed to possible scrutiny by others and fears that he or she may do something or act in a way that will be humiliating or embarrassing. For one to be socially phobic, exposure to the feared situation must provoke anxiety and the person must recognize this anxiety as irrational (although this may be absent in children). If another disorder is present, the social phobic fear is unrelated to it. For instance, if a person has a history of panic attacks, having a panic attack must not be the sufferer's fear. Sufferers are typically more self-conscious and self-attentive than others. As a result, social phobics tend to limit or remove themselves from situations where they may be subject to evaluation. Sufferers often recognize their fear is excessive or irrational, yet can't seem to break out of the cycle. As such, the diagnosis of social anxiety disorder is made only when the fear leads to avoiding occupational functions, social activities, or relationships with others.

Mental health professionals often distinguish between generalized and specific social anxiety disorders. People with generalized social anxiety have great distress with most or all social situations. A study by Stanford University established that distress was more likely when social encounters were unfamiliar, involved power or status differences, difference in gender, or the presence of a group of people. Those with social anxiety disorder may experience anxiety only in a few situations. For example the most common social phobia is glossophobia, the fear of public speaking or fear of performance, known as stage fright. Other examples of specific social phobias include fears of writing in public (scriptophobia) and using public restrooms (paruresis).

There is much debate concerning the relationship between social anxiety disorder and shyness. Shyness is not a criterion for social anxiety disorder. People with social anxiety disorder may be quite comfortable with certain people or many people, but still feel intense anxiety in specific social situations. Child psychologist Samuel Turner provides a summary between shyness and social anxiety disorder. Both share several features: negative cognitions in social situations, heightened physiological reactivity, a tendency to avoid social situations, and deficits in social skills. Negative cognitions include fear of negative evaluation, self-consciousness, devaluation of social skills, self-deprecating thoughts, and self-blaming attributions for social difficulties. Social anxiety disorder is distinct from shyness in that it has a lower prevalence in the population, follows a more chronic course, is more functionally debilitating, and has a later age of onset. There are problems with these kinds of comparisons. It may be that the differences between them are quantitative rather than qualitative.

Social anxiety disorder should not be confused with panic disorder. Sufferers of panic disorder are convinced that their panic comes from some dire physical cause, and often go to the hospital or call for an ambulance during or after their attacks. Social anxiety sufferers may experience a panic attack when triggered, but they are aware that it is extreme anxiety they are experiencing, and that the cause is an irrational fear. Few social phobics would willingly go to a hospital in that instance because they fear rejection and judgment by authority figures (such as the medical staff). The general form of social anxiety is sometimes incorrectly called generalized anxiety disorder. The principal difference between the two is that social anxiety disorder deals with anxiety in a social setting, while generalized anxiety disorder is extreme anxiety for any situation (work, school, et al.), not necessarily one involving other people

Cognitive aspects - In cognitive models of social anxiety disorder, social phobics experience dread over how they will be presented to others. They may be overly self-conscious, pay high self-attention after the activity, or have high performance standards for themselves. According to the social psychology theory of self-presentation, a sufferer attempts to create a well-mannered impression on others but believes he or she is unable to do so. Many times, prior to the potentially anxiety-provoking social situation, sufferers may deliberate over what could go wrong and how to deal with each unexpected case. After the event, they may have the perception they performed unsatisfactorily. Consequently, they will review anything that may have possibly been abnormal or embarrassing. These thoughts do not just terminate soon after the encounter, but may extend for weeks or longer. Those with social anxiety disorder tend to interpret neutral or ambiguous conversations with a negative outlook.

Behavioral aspects - Social anxiety disorder is a persistent fear of one or more situations in which the person is exposed to possible scrutiny by others and fears that he or she may do something or act in a way that will be humiliating or embarrassing. It exceeds normal "shyness" as it leads to excessive social avoidance and substantial social or occupational impairment. Feared activities may include almost any type of social interaction, especially small groups, dating, parties, talking to strangers, restaurants, etc. Physical symptoms include "mind going blank", fast heartbeat, blushing, stomach ache. Cognitive distortions are a hallmark, and learned about in CBT (cognitive-behavioral therapy). Thoughts are often self-defeating and inaccurate.

According to psychologist B.F. Skinner, phobias are controlled by escape and avoidance behaviors. For instance, a student may leave the room when talking in front of the class (escape) and refrain from doing verbal presentations because of the previously encountered anxiety attack (avoid). Minor avoidance behaviors are exposed when a person avoids eye contact and crosses arms to avoid recognizable shaking. A fight-or-flight response is then triggered in such events. Preventing these automatic responses is at the core of treatment for social anxiety.

Physiological effects - Physiological effects, similar to those in other anxiety disorders, are present in social anxiety disorder. Faced with an uncomfortable situation, children with social anxiety may display tantrums, weeping, clinging to parents, and shutting themselves out. In adults, it may be tears as well as experiencing excessive sweating, nausea, shaking, and palpitations as a result of the fight-or-flight response. It should be strongly emphasized that the term "lacrimation" refers to eye watering, not crying. The walk disturbance may appear, especially when passing a group of people. Blushing is commonly exhibited by individuals suffering from social anxiety disorder. These visible symptoms further reinforce the anxiety in the presence of others. A 2006 study found that the area of the brain called the amygdala, part of the limbic system, is hyperactive when patients are shown threatening faces or confronted with frightening situations. They found that patients with more severe social anxiety showed a correlation with the increased response in the amygdala.