Sex Differences in Age at Onset and Presentation of Trichotillomania and Trichobezoar: A 120-Year Systematic Review of Cases.

Trichotillomania (hair-pulling disorder) has high female preponderance. It has been suggested that onset in early childhood represents a distinct developmental subtype that is characterized by higher prevalence of males compared to later onset cases. However, the empirical literature is scarce. We conducted a systematic review of case reports to examine the distribution of age at onset/presentation in males and females with trichotillomania or trichobezoar (a mass of hair in the gastrointestinal tract resulting from ingesting hair). We identified 1065 individuals with trichotillomania and 1248 with trichobezoar. In both samples, males, compared to females, had earlier age at presentation and greater proportion of cases in early childhood. These sex differences remained after potential confounding variables were accounted for. The results showed similar sex differences for age at onset, which was reported in 734 and 337 of the trichotillomania and trichobezoar cases, respectively. The findings may reflect neurodevelopmental underpinnings in early childhood trichotillomania.