Risk factor patterns define social anxiety subtypes in adolescents with brain and clinical feature differences.

Social anxiety disorder (SAD) is one of the most common psychiatric disorders in adolescents. The heterogeneity of both symptoms and etiology is an essential source of difficulties in the treatment and prevention of SAD. The study aimed to identify subtypes of adolescent SAD based on etiology-related phenotype dimensions and examine symptom and brain associations of the subtypes. We used a deeply phenotyped sample (47 phenotype subscales from 13 measures) of adolescents with SAD (n = 196) and healthy controls (n = 109) to extract etiology-relevant risk factors, based on which we identified subtypes of SAD. We compared the subtypes on clinical characteristics and brain morphometrics and functional connectivity, and examined subtype-specific links between risk factors, brain aberrance, and clinical characteristics. We identified six etiology-relevant risk factors and two subtypes of adolescent SAD. One subtype showed mainly elevated negative emotionality trait and coping style and diminished positive emotionality trait and coping style, while the other additionally had significantly high environmental risk factors, more severe impairments in social functioning, and significant abnormalities in brain structure and function. There were subtype-specific links between the risk factor profiles, brain aberrance, and clinical characteristics. The finding suggests two etiology-based subtypes of adolescent SAD, providing novel insights to the diversity of pathological pathways and precise intervention strategies.