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.
Keywords: 2D:4D digit ratio, Neurodevelopment, Prenatal hormonal
exposure, Tic disorders, Yale Global Tic Severity Scale