Youth with selective mutism: a nationwide patient registry study.

Nationwide studies of selective mutism (SM) are scarce. This study examined the prevalence of SM in Child and Adolescent Mental Health Services (CAMHS), referral reasons, occurrence of additional mental disorders, and psychotropic medication use in a nationally representative clinical population. The sample comprised all youth referred to CAMHS and registered with a diagnosis of SM in the Norwegian Patient Registry from 2008 to 2022. In total, 1591 youth with SM were identified, with a female-to-male ratio of 2:1. The mean age at first CAMHS referral was 9.1 years (SD 4.0). Boys were referred significantly earlier than girls (8.8 years (SD 4.0) versus 9.3 years (SD 4.0, t = -2.29, df 1589, p = .02)). The main referral reasons were suspected anxiety and affective disorders. The mean age at SM diagnosis was 10.1 years (SD 4.2); boys were diagnosed slightly earlier than girls (9.8 years (SD 4.2) versus 10.2 years (SD 4.2, t = -2.12, df 1589, p = .03)). Additional mental disorders were diagnosed in 51.4% at a mean age of 13.2 years (SD 3.7), most commonly anxiety disorders (33%; ICD-10 F40-F41, F93). Learning difficulties were diagnosed in 9% at a mean age of 11.0 years (SD 4.0). Nearly one-third (31.5%) were prescribed psychotropic medication, mainly during adolescence, with selective serotonin reuptake inhibitors (SSRIs) being most common. This nationwide study demonstrates a relatively late age at SM diagnosis and frequent additional mental disorders. Though further longitudinal research is warranted, findings suggest that earlier diagnosis with earlier specialist care for anxiety may be needed to improve outcomes in SM, especially in girls.