Burçin Şeyda Karaca, Gonca Özyurt
These findings reveal pronounced group differences in absolute finger lengths between children and adolescents with tic disorders and healthy controls; however, 2D:4D ratios were not directly associated with tic severity. The results suggest that the 2D:4D ratio may be more appropriately considered a supportive biological marker reflecting neurodevelopmental vulnerability, rather than a robust or specific clinical indicator for tic disorders.
OBJECTIVE: This study investigates the association between tic disorders in children and adolescents and the 2D:4D digit ratio (the ratio of index to ring finger lengths), a widely recognized indirect marker of prenatal hormonal exposure. Given the higher prevalence of tic disorders among males, we assessed whether 2D:4D ratios are related to both the presence and severity of tic disorders.
METHODS: This observational, cross-sectional study included 57 children and adolescents diagnosed with tic disorders according to DSM-5 criteria and 52 age and sex-matched healthy controls. The lengths of the second (2D) and fourth (4D) digits on both hands were measured using digital calipers, and 2D:4D ratios were calculated accordingly. Tic severity was evaluated using the Yale Global Tic Severity Scale (YGTSS). Statistical analyses included group comparisons, correlation analyses, and logistic regression models.
RESULTS: The tic disorder group exhibited significantly shorter absolute 2D and 4D finger lengths bilaterally compared to healthy controls. With respect to digit ratios, the right-hand 2D:4D ratio was significantly higher in the tic disorder group compared to controls (p <0.01), while no significant difference was observed for the left-hand 2D:4D ratio. No significant correlations were identified between rightor left-hand 2D:4D ratios and total or subscale scores of the YGTSS. Logistic regression analysis demonstrated that an increase in the righthand 2D:4D ratio was inversely associated with the likelihood of a tic disorder diagnosis, whereas age and sex were not significant contributors to the model.
CONCLUSIONS: These findings reveal pronounced group differences in absolute finger lengths between children and adolescents with tic disorders and healthy controls; however, 2D:4D ratios were not directly associated with tic severity. The results suggest that the 2D:4D ratio may be more appropriately considered a supportive biological marker reflecting neurodevelopmental vulnerability, rather than a robust or specific clinical indicator for tic disorders.