Large epidemiological studies have established that SAD is one of the most common psychiatric disorders. The National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), for example, recently found a lifetime prevalence of 5.0 % and 12-month prevalence of 2.8 % for SAD among 43,093 adults in the United States (Grant et al. 2005). A recent review (Fehm et al. 2005) of 21 community studies in European countries found median lifetime and 12-month prevalence rates of SAD of 6.7 % and 2.0 %, respectively. The WHO World Mental Health (WMH) Survey Initiative (Stein et al. 2010) found that lifetime social fears are common in both developed (15.9 %) and developing (14.3 %) countries; however, lifetime SAD has a higher prevalence in developed countries (6.1 %) compared to developing countries (2.1 %).

Mean age of onset is in the mid-teens, and onset after age 30 is uncommon (Schneier et al. 1992). Although prevalence of SAD is greatest among young adults, for many sufferers the disorder is chronic. Prevalence is also greater among persons who are less educated and those who are single (Schneier et al. 1992; Blanco et al. 2011). Additionally, SAD is usually accompanied by comorbid disorders, such as depression, substance abuse, or other anxiety disorders, which can further impair functioning (Fehm et al. 2005).

SAD has been shown in many studies to be associated with impairment and disability. SAD increases the risk of dropout from school, work absence, unemployment, and utilization of social welfare, causing significant financial costs for society (Lecrubier et al. 2000). When compared with persons with no psychiatric disorder, having SAD is associated with financial dependency and increased rates of suicidal ideation (Schneier et al. 1992; Cougle et al. 2009; Olfson et al. 2000). Katzelnick et al. (2001) examined costs and impairment associated with SAD in a community sample of 1,017 subjects. Subjects with generalized SAD and no comorbidity reported significant impairment in terms of family relations, romantic relationships, social network, and ability to moderate alcohol use, compared to those with no diagnosis. Generalized SAD was associated with significantly lower health-related quality of life, work productivity and earnings, and greater utilization of health services. During the month before participating in the survey, 12.2 % of subjects with SAD reported having had thoughts of suicide.

Several subtypes of SAD have been described. Generalized SAD has been the most studied subtype, and it was defined in DSM-III-R and DSM-IV by fear of most social situations (American Psychiatric Association 2000). Persons with generalized SAD tend to have more severe symptoms and impairment, and are more likely to seek treatment. The National Comorbidity Survey (1998) reported significantly greater comorbidity among persons with SAD and at least one feared situation other than public speaking. Persons with SAD involving three or more social fears also evidenced greater chronicity and impairment. Most persons with the nongeneralized type of SAD, or with the performance type newly described in DSM-5 (American Psychiatric Association 2013), have predominantly fears of performance such as public speaking, with relative sparing of social interaction situations.

Prevalence of SAD among women has been found to be elevated relative to the rate in men in most community studies. In the NESARC study (Grant et al. 2005), 12-month prevalences were 2.1 % for men and 3.3 % for women; lifetime prevalences were 4.2 % for men and 5.7 % for women. Similarly, elevated rates of SAD in women have been reported in European samples (Fehm et al. 2005). The female-to-male ratio of 1.35 for lifetime prevalence of SAD in the NESARC study (Xu et al. 2012) is within the range of previous epidemiological studies (Kessler et al. 1994; Ohayon and Schatzberg 2010). The ratio is lower, however, than gender ratios reported for other anxiety disorders in major epidemiologic studies, which have ranged from 1.8 for generalized anxiety disorder in the National Comorbidity Survey (Kessler et al. 1994) to 2.7 for agoraphobia in the Epidemiological Catchment Area (Bourdon et al. 1988). Xu et al. (2012) also found that men with SAD were more likely than women with SAD to have never been being married, or to be separated or divorced.

Crome et al. (2012) sought to investigate whether the preponderance of women among those diagnosed with SAD by community surveys was due to a response bias of women being more likely to respond positively to questions about SAD. The study involved a subsample of 1,755 participants in the Australian National Survey of Mental Health and Wellbeing who had reported at least one social fear. A series of factor analyses suggested that men and women tended to respond comparably to SAD diagnosis items. Men, however, tended to report lower levels of physical symptoms at low levels of social fear, compared to women. Overall, findings supported the legitimacy of higher rates of SAD among women.

Gender differences among persons with SAD were examined in a recent cross-sectional study by MacKenzie and Fowler (2013) of 36,984 Canadians aged 15–80 years. Men with SAD were more likely to be single, unattached, and living alone than women with SAD. Women with SAD were more likely to be widowed, separated, or divorced, and they were more likely to be a single parent. Women also reported poorer mental health and greater stress levels than men with SAD.

Several studies have examined the course of SAD in women and men. Gender differences in prevalence of SAD were small in the pre-school and elementary school years but increased after the age of 12, according to a retrospective study of 8,116 Canadian adults (DeWit et al. 2005). For persons with the generalized subtype of SAD, at every age from pre-school to early adulthood, the proportion of females who had developed SAD exceeded the proportion of males. In contrast, a female preponderance for the development of nongeneralized SAD began to emerge only after the age of 12. In a study of 2,128 Swedish students aged 12–14, the prevalence of SAD was 6.6 % among girls versus 1.8 % among boys (Gren-Landell et al. 2009), and 91.4 % of the children with SAD reported impairment in school functioning.

Gender differences in the prevalence of specific types of social fears have also been reported. A survey of 526 community respondents (Stein et al. 1994) showed that women reported significantly greater anxiety about public speaking, speaking to strangers, meeting new people, and dealing with people in authority, but that men and women did not differ significantly in severity of anxiety while writing in front of others, eating in front of others, or attending social gatherings. Women with SAD in the community also experienced higher rates of some social fears (Xu et al. 2012). Men and women with lifetime SAD differed significantly in rates of fear of dating (men 29.5 % vs. women 22.3 %), being interviewed (men 39.7 % vs. women 52.0 %), and speaking at a meeting (men 69.4 % vs. women 74.9 %).

Several community studies have examined gender differences in comorbidity among individuals with SAD. Xu et al. (2012) found that men with a lifetime diagnosis of SAD were more likely to have lifetime alcohol abuse and dependence, drug abuse and dependence, pathological gambling, conduct disorder, and antisocial personality disorder. Women were more likely to suffer from mood and anxiety disorders, except bipolar I and II disorders, which had the same probability to be diagnosed in both genders. Women with SAD were thus more likely to have comorbid internalizing disorders and less likely to have comorbid externalizing disorders.

Rodebaugh et al. (2012) examined the impact of psychiatric disorders on friendship quality by gender, among participants in the National Comorbidity Survey (Kessler et al. 2004). SAD had a negative effect on friendship quality in both men and women, although in men this was exacerbated when comorbid generalized anxiety disorder was present, whereas in women comorbid major depression was associated with an additional negative impact on friendship quality.

In adolescents, a Finnish study (Väänänen et al. 2011) found gender differences in the longitudinal relationship between SAD and depression. In this population-based prospective study of 15-year-olds (N = 2,038), SAD at baseline increased the risk for depression over the next 2 years in boys only. Among adolescent girls, baseline depression was a risk factor for subsequent SAD. Wu and colleagues (2010) looked at gender differences in the relationship between SAD and substance use among 781 adolescents in the community. In girls, there was a trend for SAD to be associated with lower rates of substance use. In boys, however, cigarette smoking was significantly associated with SAD.

Buckner and colleagues have further investigated the interactions between SAD, substance use disorders, and gender. In one study, Buckner et al. (2006) examined the relationship between cannabis use disorder, SAD, and peer influence in 123 male and female undergraduates. Symptoms of SAD were significantly related to symptoms of cannabis use disorder only among women. This relationship was further moderated in women by the influence of peers and their use of alcohol and cannabis. Specifically, women with more SAD symptoms were particularly prone to problematic cannabis use and more vulnerable to influences from peers. In another study (Buckner and Turner 2009), SAD was a risk factor for development of alcohol use disorders among women only, in a 3-year prospective study of 1,803 young adults from the National Comorbidity Survey. The risk of women developing an alcohol use disorder was further moderated by lower family cohesion and more adverse family relations.

In respect to treatment seeking, individuals with SAD typically do not seek treatment until their late 20s to 30s, despite a mean age of onset of SAD in early adolescence (Mannuzza et al. 1995). Xu et al. (2012) reported that among persons with lifetime SAD in the community, men and women did not differ in their overall probability of treatment seeking for SAD. Lifetime rates of treatment seeking for SAD were 17.9 % for men and 19.2 % for women; lifetime rates of use of medication for SAD were 8.8 % for men and 12.4 % for women. Thus, over 80 % of individuals with SAD in the NESARC study had received no treatment for it, and the mean age at first treatment was 27.2 years (Grant et al. 2005).

A growing number of neuroimaging studies of SAD during the last decade have attempted to elucidate the neural mechanisms of the disorder. The most consistent findings have demonstrated increased activation of the amygdala and surrounding cortices, including the hippocampus (Schmidt et al. 2010) in persons with SAD during exposure to emotional threat stimuli, such as angry faces. Functional neuroimaging studies have reported that exaggerated amygdala activation is positively correlated with symptom severity and decreases after successful treatment (Furmark et al. 2002). Furthermore, treatment studies indicate that both pharmacotherapy and psychotherapy of SAD normalize activation in the amygdala and related structures (Goldin and Gross 2010).

A variety of neurotransmitter systems, including serotonin, norepinephrine, dopamine, GABA, and glutamate have evidenced abnormalities in SAD. Dysfunction of the hypothalamic-pituitary-adrenal axis has also been reported. Few of these studies, however, have assessed outcome by gender. In a study of 53 patients seeking treatment for SAD, however, heart rate variability, an index of autonomic control, was reduced in SAD overall, but also more specifically among women with SAD (Alvares et al. 2013). This may indicate a greater sensitivity to the effects of social anxiety on parasympathetic nervous system reactivity in women.

The prototypical onset of SAD in early adolescence has raised questions about the impact of physiological and psychosocial changes of puberty. Deardorff et al. (2007) assessed 106 children aged 9–11 for pubertal status and social anxiety. Advanced pubertal development was associated with higher levels of social anxiety among girls only, consistent with findings of gender differences in depression.

Family studies have shown that SAD is familial (e.g., Lieb et al. 2000), with first-degree relatives of adults with SAD being three times as likely as relatives of control subjects to suffer from SAD (Fyer et al. 1995). Some studies have further suggested that the generalized subtype may be more familial than the specific subtype (Stein et al. 1998). Part of this familial risk is attributable to genetic heritability, and twin studies suggest that the underlying structure of the genetic and environmental risk factors is similar between men and women (Hettema et al. 2005).

Genetic influences on the development of SAD may be specific to the disorder, or may be related to relatively nonspecific factors, such as negative affect. A highly heritable temperamental trait that is thought to predispose individuals to SAD is behavioral inhibition, characterized by a consistent pattern of behavioral, physiological, and emotional responses to unfamiliar people and novel situations. Inhibited children usually respond with restraint and withdrawal to novel objects and situations, and they are usually shy with unfamiliar people (Kagan 1994). In a longitudinal study of 238 children, girls evidenced greater inhibition and afternoon cortisol levels as preschoolers, and they were at greater risk for developing chronic high inhibition and SAD (Essex et al. 2010).

Psychosocial factors, such as parenting, peer interactions, and culture can play an important role in the development of SAD. Socially anxious adults often report having experienced negative parenting qualities such as overprotection, lack of warmth, excessive concern with the opinion of others, and rejection during their childhood (Caster et al. 1999). Adults with SAD are more likely to recall their parents as excessively protective and controlling (Rapee and Melville 1997).

Childhood maltreatment has been associated with symptom severity, reduced quality of life, and impaired functioning in adults with SAD (Bruce et al. 2012). Data were obtained from 156 treatment-seeking patients with a primary diagnosis of generalized SAD who had a history of childhood trauma. Childhood emotional abuse, emotional neglect, and physical neglect, but not sexual or physical abuse, predicted more severe symptoms in patients with SAD. Of the maltreatment subtypes, emotional abuse was the strongest predictor of severity of social anxiety, disability, and decreased quality of life. Other studies have linked SAD with early sexual abuse. Feerick and Snow (2005) examined the relationship between childhood sexual abuse and SAD in a sample of 313 undergraduate women. In this study, 31 % of the women reported that they had experienced some form of sexual abuse in childhood. Women with a history of sexual abuse reported more symptoms of anxiety and distress in social situations than women who had not experienced sexual abuse. Those women whose abuse included actual or attempted intercourse had higher scores for social avoidance than women who had not been abused, or who had experienced other forms of abuse such as exposure or fondling. In addition to the type of abuse experienced, earlier age of onset of abuse also significantly predicted greater avoidance and distress in adulthood.

McGabe et al. (2003) found a relationship between bullying in childhood and adolescence and SAD later in life. This study assessed the relationship between childhood memories for teasing and SAD in adulthood. Five hundred and fourteen undergraduates completed a questionnaire that measured the degree to which people recall having been teased during childhood and also completed established measures of SAD. Men and women recalled having been teased with similar frequency; however item-by-item analysis suggested that boys had a more negative experience with teasing than girls (e.g., men remembered having been teased about not doing well at school and being a troublemaker more often than women).

Parents impact their children’s social interactions directly by arranging play dates, overseeing play situations, and supervising peer interactions (Masia and Morris 1998). Thus, parents’ relationships and skills related to their child’s development could influence their social and emotional development. Maternal SAD has been shown to significantly predict SAD in offspring (Bögels et al. 2001). Although most of the research on parenting has focused on mothers, paternal influences may also be important (Greco and Morris 2002). The influence of fathers is smaller, however, and more significant later in the child’s life (Connel and Goodman 2002).

Contemporary theories of SAD emphasize the role of cognitive processes in the maintenance of the disorder, and a theoretical model has been proposed (Clark and Wells 1995). According to this model, individuals with SAD are apprehensive in social situations because they perceive the social standard as being high and they doubt that they are able to make a favorable impression, which will result in disastrous consequences (Leary 2001). This leads to a further increase in apprehension and increased self-focused attention, which triggers a number of additional cognitive processes (Hirsch and Clark 2004). As a result, the individual with SAD anticipates social mishaps and engages in avoidance and/or safety behaviors (Wells et al. 1995).

Avoidance and safety behaviors play an important role in the maintenance of SAD, because they reinforce social fears and diminish opportunities for positive social experiences. Individuals with SAD engage in safety behaviors in social situations in order to minimize negative evaluations from others; typical examples of safety behaviors include avoiding eye contact, monitoring one’s speech, and avoiding pauses while talking (Kim 2005). When safety behaviors are used, the individual attributes the nonoccurrence of feared catastrophes to the implementation of the safety behavior. Therefore, safety behaviors are maladaptive, because they prevent exposure to the feared social situations and processing of the emotional information, for example, individuals who speak little in social encounters because they fear negative evaluation are less likely to receive positive feedback from others (Clark 2001).

In addition to the previously mentioned cognitive and behavioral factors that contribute to the development and/or maintenance of SAD, recent evidence also suggests a contributing role of exaggerated negative emotional reactions, attenuated positive emotional reactions, and emotion regulation difficulties in producing functional impairment (Goldin et al. 2009). While there are numerous ways of affecting one’s emotional experiences, two specific strategies have received substantial scientific attention: cognitive reappraisal and emotion suppression. Cognitive reappraisal involves changing one’s perspective to downplay or enhance a situation’s emotional impact and altering the interpretation of emotional information (Gross 2002). Emotion suppression involves inhibiting emotional responses to a situation by downregulating the expression of the emotion. People with SAD report frequently suppressing both positive (Werner and Gross 2010) and negative emotions (Erwin et al. 2003). Excessive use of suppression can have negative impact on the positive experiences of people with SAD. A meta-analysis of 19 studies found a stable, moderate relationship between SAD and less frequent and intense positive emotions (Kashdan 2007). Maladaptive emotion regulation contributes to the adverse impact of social anxiety on positive events in daily life, and people high in SAD report using more positive emotion suppression (Turk et al. 2005). One reason for this may be that individuals with SAD find expressing positive emotions in social-evaluative situations to be uncomfortable (Kashdan et al. 2011). While suppressing positive emotions may help individuals with SAD to minimize social attention towards them, it may also contribute to sustained anxiety and avoidance of interactions.

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (American Psychiatric Association 2013), offers operationalized criteria for the diagnosis of psychiatric disorders by clinicians and researchers. In 2013, the publication of the Fifth Edition of the DSM incorporated several changes to the criteria for SAD (Heimberg et al. 2014). First, while “social anxiety disorder” had been previously considered a secondary name for “social phobia,” it is now recognized in DSM-5 as the principal name for this diagnosis, because it was felt to better convey the sense of pervasiveness and impairment associated with the disorder. The description of primary fear in SAD was broadened beyond showing embarrassing or humiliating anxiety symptoms, to include fear of showing symptoms that will be negatively evaluated. Whereas DSM-IV required that the person must recognize that the fear is excessive or unreasonable, DSM-5 instead requires that the fear be out of proportion to the actual threat, and encourages consideration of cultural context. Another change was to allow the diagnosis of SAD to be made in the presence of another embarrassing medical condition, as long as the social anxiety symptoms are either unrelated to the medical condition or excessive, in the clinician’s judgment.

DSM-5 criteria for SAD require two key features:

In addition, DSM-5 criteria require that the social situations must almost always provoke fear or anxiety, and the situations are avoided or endured with fear and anxiety. The fear or anxiety must be out of proportion to the actual threat posed by the social situation. Symptoms must have persisted for at least 6 months or more, and they must cause clinically significant distress or impairment in social or occupational functioning. Finally, social anxiety and avoidance cannot be due to the physiological effects of a drug of abuse, a medication, or another medical condition. It also must not be better explained by the symptoms of another mental disorder, such as when social avoidance occurs in depression due to lack of social interest. Social anxiety disorder can be diagnosed in the presence of another potentially embarrassing medical condition, such as essential tremor or disfigurement from burns, if the fear, anxiety, and avoidance are unrelated to the medical condition or is excessive.

The International Classification of Disease, 10th Edition (ICD-10) criteria for social phobia, developed by the World Health Organization (WHO) are as follows:

All of the following criteria should be fulfilled for a definite diagnosis: