Journal of Occupational

Introduction
Stuttering is a disorder in the normal fluency and time patterning of speech [1]. Craig A (2002) showed that the prevalence of stuttering was about 1%, and its rate of incidence was 4-5% across the entire life span in the state of New South Wales, Australia [2–4]. According to the results, the prevalence of stuttering was 0.72% across the whole population, with the highest and lowest prevalence rates having been in younger children (1.4–1.44) and in adolescents (0.53), respectively. In addition, the male-to-female ratio ranged from 2.3:1 in younger children to 4:1 in adolescents, with the ratio of 2.3:1 registered across all ages. Household members were also interviewed by asking whether anyone in the household had ever stuttered. If the answer was 'yes', the same corroborative questions would be asked. These data along with the prevalence data provided an estimate of the incidence or risk of stuttering, which ranged from 2.1% in adults (21–50 years old) to 2.8% in younger children (2–5 years old), and to 3.4% in older children (6–10 years old). In addition, the prevalence of total speech disorders was 14.8% in the Iranian community, among whom 13.8% had a speech sound disorder, 1.2% had the stuttering disorder, and 0.47% had a voice disorder [5].
Negative consequences of stuttering start from age 4-5 and continues throughout the life [6, 7]. These problems become more complex in adolescence, which include anxiety, social communication, and educational problems [8, 9]. People with stuttering, due to the listeners' negative reactions and negative attitude to their speeches, demonstrate avoidance behaviors, anxiety, aggression, with conflicts existing in most of them [10, 11]. These negative experiences lead to the feelings of embarrassment, shame, and lack of academic achievement. The probability of having psychological, behavioral, and emotional disorders, especially anxiety, is higher among people who stutter [12–14].
The psychosocial aspect of stuttering is one of the major components of this disorder that needs special attention in the course of treatment. Negative thoughts and reactions against stuttering start from childhood when a child begins to notice their speech differences [15, 16]. Negative attitudes towards communication and even the “self” develop when a child experiences stuttering and stigmatization in the society. Stuttering is accompanied by the destructive feelings of frustration, anger, guilt, and humiliation [17]. Because of social stigmas, PWS could have a lower chance for employment and higher education [18].
The degree of the impact of stuttering on a person’s life differs among individuals. Some people encounter serious problems with communication competence, self-confidence, romantic relationships, and personality attributes [19–21]. The effects of stuttering on personality development have been studied in three countries, including Germany, Australia, and Iran. Based on these studies, PWS has a higher agreeableness. Jafari et al (2015) argued that the higher level of agreeableness in PWS would probably be a self-defense mechanism against being bullied and teased [20]. This study showed the importance of social stigmatization in personality development, thereby exerting an effect on many aspects of an individual’s life.
Because of the aforementioned impacts of stuttering on PWS’s everyday life and psychological profiles, many studies have been carried out on mental disorders among PWS.
Per A. Alm (2014) reviewed several studies on comparing mental disorders between PWS and PWNS [22]. In this study, no significant differences were observed between PWS and PWNS in shame, sadness, social phobia, social functioning, as well as psychological and emotional activities; however, stronger impulsive behaviors and greater lack of control were observed among PWS than in PWNS. Their review of studies revealed that negative social assessments were among the major reasons for differences between PWNS and PWS. In addition, their review showed that the cognitive behavioral therapy (CBT) was one of the most effective treatments for mental disorders in PWS, which showed a clear effect on social anxiety and psychological wellbeing in this population. However, this study did not show any effects on speech fluency. Another result from their review was that improved fluency after the fluency shaping therapy was associated with anxiety reduction. Studies on psychological treatments focusing on anxiety have verified their positive effects on psychological wellbeing but have shown little or no effect on speech fluency [22].
Kefalianos, Onslowcm Blockd, Menziesc, and Reilly (2012) found out that stutterers' temperament would not lead to anxiety [23]. Some stuttering preschool children experience negative peer responses and difficulties in social interactions with their peers as a consequence of their stuttering [10]. Although results of research on adaptability are not the same, new research using observations rather than parent assessment questionnaires suggests that CWS have lower adaptability and a lower capacity for regulating their attention than CWNS [23].
Iverach, O’Brian, Kefalianos, and Rreilly (2013) reviewed several studies to determine the scope of research on the timing of anxiety onset in stuttering. Researchers claim that anxiety in stuttering people might increase over time until exceeding normal limits in adolescents and adults [24].
Iverach and Rapee (2013) reviewed some studies to determine the level of social anxiety in people who stutter and to suggest that research accomplished prior to the turn of the century produced evidence of raised anxiety in people who stutter [25]. Because of the proven impact of stuttering on a person’s life, psychosocial wellbeing, and the quality of life, studying mental disorders in PWS is of great importance in treating stuttering. Against this background, this study aims to review three common mental disorders, including anxiety, social phobia, and depression among PWS [25].
 
Materials and Methods
In this paper, to answer an old question, there was a need for a wide range of relevant papers. To this end, we searched keywords with stutter, including stutter and anxiety, stutter and social anxiety, stutter and depression, as well as stutter and mental disorders and suicide on ScienceDirect, Springer, Google Scholar, and Scopus from 1985 to 2020. A total of 34 relevant research papers were selected from among 321 papers for this study. For anxiety, social anxiety, and depression, 13, 12, and 9 papers were selected, respectively.
 
Results
Anxiety: Anxiety is probably the most common mental disorder among people who stutter [24, 26]. The majority of studies on mental disorders in PWS have been conducted on anxiety. Given the role of speaking in academic achievement and job success, it is evident that anxiety is common in stutterers [27, 28]. Despite numerous studies, the cause-effect relationship between stuttering and anxiety has not been clearly explored [8, 29]. The results obtained in research on anxiety among children with stuttering are equivocal [24]. Some research reports anxiety as a common disorder among children and adolescents who stutter [30–33], yet some other research does not establish this relationship [34–38]. Boys tend to hide their anxiety about their stuttering [36]. This could be one of the reasons for the dual results of research on stuttering anxiety, with the worse outcome being produced perhaps due to the fact that these people are less likely to undergo treatment [39–42]. Unfortunately, most research on stuttering and anxiety has been carried out on adults, while the most likely occurrence period of mental disorders, especially anxiety, is during adolescence [43]; however, in few studies on mental disorders in people with stuttering during adolescence, anxiety has been considered one of the most common psychiatric disorders [31–33, 44].

Social phobia: Social anxiety is a chronic mental disorder characterized by severe fear from others in social situations or by fear from one’s performance being assessed by others [1]. The prevalence of social anxiety in the US adult community is 8-13%, which is one of the major psychiatric disorders in the world [10, 45–47]. It is a common disorder in PWS [28, 48–51], which also exists in teenage stutterers [24]. This disorder could also be observed among children aged 7 to 12 [19]. People seeking treatment for stuttering are more likely to show symptoms, such as social phobia [52]. In some studies, 22-60% of PWS suffered from social anxiety [25, 53–56]. Suffering from social anxiety could negatively affect treatment outcomes [28].
Results of a comparison made between stuttering and non-stuttering individuals indicate that the probability of being diagnosed with social phobia, anxiety, and the general anxiety disorder is several times higher in PWS than in PWNS. Future research should assess the impacts of these mental disorders on treatment outcomes [28].
Shame, guilt, poor social interactions, and fear of speaking, especially among strangers, are common problems facing stuttering people [57–62]. It seems that social anxiety exacerbates in stuttering people with childhood experiences, communication problems, and negative outcomes. In addition, their entire life could be a source of social anxiety. Social anxiety intensifies behavioral weaknesses in social situations and reduces social interactions [63–65].
There are many reasons for the connection between stuttering and social anxiety. Stuttering is accompanied by negative social factors and psychological disorders in life [66, 67]. These negative consequences start in early childhood, for children are prone to being ridiculed, harassed, avoided, bullied, and teased by their peers [68–70]. Negative consequences are intensified during school hours due to more social interactions and the need for speaking to be included in the community. Against this background, stuttering people are more likely to be rejected by peers and to be excluded from the society and social connections [71–73].
Not surprisingly, most stutterers report that stuttering exerts lots of negative effects on their academic performance during the academic year as well as on their social and emotional performance [74–76]. There are many reasons why stuttering people experience a high level of social anxiety, and there are many ways for
growing social anxiety [77–79] during childhood and adolescence [80, 81]. Clinical psychologists suggest many social, environmental, biological, genetic, and psychological reasons for the sources of social anxiety, which in combination show the complexity of the disorder [82–84].
Some of these factors, such as social factors, could be stronger in PWS. CWS could be more exposed to negative reactions from peer groups, such as ridicule, rejection, and harassment [77, 81, 84]. These reactions reduce social interactions, age-appropriate social interactions, and social skills, yet they increase the chance of experiencing social anxiety [81].
There is not enough research on examining factors leading to the emergence and growth of social anxiety in stuttering people. The main problem to be assessed is that PWS could become more anxious when they are taken into consideration, and the other major problem is that they react when they are evaluated. They might not react under normal conditions; therefore, this point must be taken into account when evaluating social situations in PWS [85].

Depression: The correlation between depression and stuttering has not yet been thoroughly investigated, and research on this subject in incomplete. However, the comparison of mean depression scores in PWS and PWNS shows that the mean depression scores for stutterers are higher [86–88]. In addition, depression could occur in PWS, based on DSM 4 (IV-TR) [89]. There is a strong positive correlation between depression and anxiety [90]. Besides, the relationship between depression and stuttering has been shown in past research [88].  
Depression itself has several types, with their common features being sadness, lack of pleasure, attenuated appetite, reduced or increased sleep, and impaired functions [1]. Research on depression in stutterers has received contradictory results as well. Although some studies have reported high levels of depression in stutterers [91–93], others have failed to prove PWS suffer from more serious depression than their peers [94, 95]. In Miller and Watson's study, the average depression scores for stutterers were higher than those for non-stutterers. Research reports that people who stutter are more likely to suffer from mood disorders and depression [92]. However, research reported a negative correlation between stuttering and depression [96, 97].
Some studies used other tests to measure depression. Research, using the Reynolds Adolescent Depression Scale, showed no
significant differences among stuttering and non-stuttering adults in depression between the two groups [93, 98].
In contrast to research conducted in Spain, stuttering students showed more significant symptoms of depression than the non-stuttering ones. In this study, clinical diagnosis was not used, but a self-report questionnaire was utilized to measure depression [10, 99].
Some research also used the personality inventory to measure depression in stutterers. Research using the Minnesota Multiphasic Personality Inventory [100] and MMPI–2 [101] showed that people who stutter had significantly higher scores of depression than those not stuttering [102, 103].
In summary, the relationship between depression and stuttering is not still well defined, with one reason for which being the non-use of an appropriate unit for measuring depression; the other reason would be the small number of the research population used in clarifying the connection between depression and stuttering [104].