Long-term outcomes of selective mutism: a systematic literature review

BACKGROUND: Selective mutism (SM) is a childhood onset anxiety disorder, and the main symptom is not speaking in certain social situations. Knowledge about the duration and long-term outcomes of SM have been lacking and the aim of this systematic literature review was to address this gap in the literature. We investigated how long SM symptoms persisted as well as other psychiatric outcomes associated with SM in later life.

METHODS: The PubMed, PsycInfo, Web of Science, Cochrane Library and Embase databases were initially searched from inception to 11 September 2023. Studies were included if they were published in English and had followed up subjects with clinically diagnosed SM for at least two years. The review followed the Preferred Reporting Items of Systematic Reviews and Meta-analyses guidelines and the protocol was registered with the Open Science Framework. The papers were assessed using the Quality Assessment with Diverse Studies tool.

RESULTS: This review screened 2,432 papers and assessed 18 studies. Seven case series studies were excluded from discussion because of the low number of subjects and the fact that their findings could not be generalized to wider populations. In the end, nine clinical cohorts and two case control studies were reviewed. These provided a total of 292 subjects and the sample sizes ranged from 11-49. The overall quality of the studies was moderate. The review found that 190 of the 243 subjects in the studies that reported recovery rates showed moderate or total improvement from SM during follow up. Other anxiety disorders were the most common psychiatric disorders later in life, although these results should be interpreted with caution. Older age at baseline and parental psychopathology might predict greater impairment, but further studies are needed to confirm these results.

CONCLUSIONS: Most subjects with SM recovered from this disorder during adolescence, but anxiety disorders were common in later life. Early detection and treatment are needed to prevent symptoms from persisting and other psychiatric disorders from developing.