Table 1 Full list and details of the cohort and case–control studies included in the systematic literature review
From: Long-term outcomes of selective mutism: a systematic literature review
Study Country | Study design Treatment provided, if any | Sample size Age at baseline | Length of follow up | Setting and diagnostic methods for mutism | Outcom Methods used to measure outcomes | Results summary at follow up | Predictors for outcomes |
|---|---|---|---|---|---|---|---|
Cohort studies | |||||||
Arajärvi, 1965 Finland [29] | Clinical cohort Psychosocial, in-patient treatment | n = 12 4–8 years | 1–10 years | Clinical | SM symptoms Questionnaires filled in by parents and one case investigated by clinician. Cognitive assessment, projective tests | 11/12 spoke in school after treatment but one still had SM symptoms |  |
Dogru, 2023 Turkey [30] | Clinical cohort Psychotherapy and/or pharmacotherapy | n = 49 5–13 years | N/A Duration of SM was 2.22 ± 1.35 years | Clinical data from patient records verified by comparing these to DSM-5 symptoms of SM | SM symptoms (K-SADS-PL), CGI | Mean duration of SM was 2.2 years. Duration of SM did not differ between males and females | Children with severe SM symptoms had a longer duration of illness and higher rates of psychiatric comorbidity |
Kamani & Monga, 2020 Canada [16] | Clinical cohort Psychosocial/ pharmacological. 74% received CBT. 45% received medication for anxiety, mainly SSRIs | n = 31 22 with SM and 9 with just social anxiety disorder 4–14 years | 2–6 years mean =  4.2 years | Clinical (from patient records). Anxiety Disorders Interview Schedule for DSM-IV | SM and social anxiety disorder Clinical, parent interview with ADIS, CGAS, SMQ and SCARED tools | 2/31 only had SM, 11/31 only had social anxiety disorder, 9/31 had both and 9/31 had neither | No difference between the types of treatment, not even for CBT Older age at baseline might predict impairment and higher rate of anxiety at follow up |
Lang et al., 2016 Israel [31] | Clinical cohort SM focused CBT | n = 24 6.40 ± 3.06 years | 2.90 ± 3.23 years | Clinical (from patient records) | SM and comorbid psychiatric disorders Clinical, structured interviews and ADIS-IV-L, CGI and SMQ | The recovery rate for SM was 84.2%. A significant decrease was observed in the levels of social phobias and specific anxiety disorder. No statistically significant improvement in other comorbidities after the follow-up period |  |
 Lowenstein, 1979 UK [32] | Clinical cohort Psychosocial | n = 21 3–8 years | 7 years | Clinical | SM symptoms Not clear | 13/21 spoke normally 6/21 had some symptoms left 2/21 had SM |  |
Oerbeck et al., 2018 Norway [33] | Clinical cohort School-based CBT intervention | n = 30 3–9 years | 5 years | Clinical | Psychiatric diagnoses Clinical assessment of the child and structured interviews from parents and teachers. SSQ, SMQ, ADIS-IV, K-SADS-PL, ILC | 21/30 in full remission 5/30 in partial remission 4/30 fulfilled diagnostic criteria for SM 7/30 children (23%) fulfilled criteria for social phobia, and 2/30 had separation anxiety disorder, 3/30 had specific phobia and 1/30 had enuresis nocturna | Older age, symptom severity at baseline and familial SM were significant negative predictors for the outcome |
Remschmidt et al., 2001 Germany [17] | Clinical cohort Psychosocial. In-patient treatment, family counselling | n = 41 8.7 ± 3.6 years | 12.0 ± 5.2 years | Clinical | SM symptoms, psychopathology symptoms, family psychopathology From patient records and 31 patients were personally assessed using standardized assessments. Interview included the Marburg Symptom Checklist and MBI or BI | 16/41 cases (39%) in remission 12/41 (29%) remarkable improvement. 8/41 (20%) mild improvement. 5/41 symptomatology remained unchanged. 10% had dysphoric mood. 19% had depression. 48% had impulsivity. 42% had severe psychopathological disturbances | Worse outcome was predicted by depressive/dysphoric mood, SM in the family, psychiatric disorders in the family, deviant parenting style were predictors |
Sluckin et al., 1991 UK [34] | Clinical cohort Psychosocial. Individual behavioural therapy or school based programs | n = 25 4–8 years | 2–10 years | Not stated, but study carried out in clinical settings | SM symptoms Follow-up questionnaires for parents and teachers and Rutter Rating Scale for teachers | 9/11 in the behavioural group improved, 5/14 in the standard program improved. (Difference in the groups was significant, p < .05) | Behavioural group treatment for better outcome. Familial psychopathology for worse outcome (p < .05) |
 Wergeland, 1979 Norway [35] | Clinical cohort 6 received individual psychotherapy, including 4 who had in-patient treatment 5 did not receive treatment | n = 11 6–12 years | 8–16 years | Clinical | SM symptoms and psychopathology Interviews with parents, patients, and siblings. If needed, information from schools, employers and hospitals were obtained | 11/11 in remission from selective mutism. Two of four children, who had received in-patient treatment, were diagnosed with a neurotic disorder and one of those four was diagnosed with a psychotic disorder at follow up |  |
Case–control studies | |||||||
Kolvin & Fundudis, 1981 UK [36] | Case–control Not specified. Received best treatment available at the time mentioned | n = 24 6–8 years | 5–10 years | Clinical | SM symptoms Not clear | 11/24 had improved: 3/24 (12.5%) markedly improved, 8/24 (33%) moderately improved and 13/24 (54%) slightly or not improved | More girls than boys in the improved group. Less parental personality problems in the improved group. No statistical analyses made for these findings due to lack of power |
 Steinhausen et al., 2006 Switzerland [18] | Case–control Not specified | n = 33 8.5 ± 3.1 years | Not reported but the mean age at follow up was 21.6 ± 3.3 years | Clinical | SM symptoms and any DSM-IV psychiatric diagnoses Clinical interview, clinical global improvement scale of SM, and psychiatric assessment by using CAPI version of the Munich-International Diagnostic Interview at follow up | All displayed some improvement. 6/33 (18.2%) were slightly improved, 8/33 (24.2%) were markedly improved and 19/33 (57.6%) were totally improved. Subjects with SM had significantly more phobic disorders (p < 0.001) than healthy controls, but no more than controls with anxiety disorders. 14/33 (42.4%) had phobic disorders. 19/33 (57.6%) had any psychiatric diagnosis. More diagnoses than in healthy controls (p = 0.005) | Severity of SM at outcome was not predicted by any tested factors. Comorbidity at outcome: any psychiatric disorder was significantly predicted by family history of taciturnity (p = .04). Phobic disorders significantly predicted by immigrant status (p = .02) |