Developmental stuttering with common and complex phenotypes.

AIM: To describe the phenotypic spectrum associated with stuttering.

METHOD: Individuals with current or resolved developmental stuttering self-referred. Surveys assessed stuttering characteristics (onset, negative impact, family history) and health (early development, other conditions). Speech and non-verbal intelligence were assessed using conversation and the Wechsler standardized scales. Sample sizes varied across assessments (n = 266-327). Latent class analysis identified unobserved groups based on assessment data.

RESULTS

A total of 327 participants (231 male, 71%) with a median age of 57 years (range: 5-90 years) were recruited, 282 of 296 (95%) with current stuttering and 14 of 296 (5%) with resolved stuttering. Onset was 4 years or younger for 187 of 322 (58%) participants; 207 of 325 (64%) had a positive family history of stuttering, 58 of 325 (18%) had developmental delay, and 38 of 264 (14%) had below average non-verbal intelligence. Common co-occurring conditions included sleep, hearing, vision, and immune conditions, migraine, anxiety, and depression. Analysis revealed two groups: 295 of 327 (90%) participants had the common phenotype and 32 of 327 (10%) had a complex phenotype, with more severe stuttering, greater negative impact of stuttering, more frequent anxiety, lower non-verbal intelligence, and neurodevelopmental disorders.

INTERPRETATION: Phenotypic analysis of a large cohort of who stutter identified 90% with a common phenotype and 10% with a complex phenotype. Both had co-occurring disorders requiring multidisciplinary support.