Association between the second-to-fourth digit ratio (2D:4D) and stuttering in children: A case-control study

Background Stuttering is a neurodevelopmental speech disorder characterized by disruptions in speech fluency, typically emerging during early childhood. Biological factors, including prenatal hormonal influences, have been suggested to contribute to its etiology. The second-to-fourth digit ratio (2D:4D) is widely considered an indirect biomarker of prenatal androgen exposure and has been associated with various neurodevelopmental and behavioral conditions. However, its relationship with stuttering remains unclear. Objective The present study aimed to examine the association between the right-hand 2D:4D digit ratio and developmental stuttering in children by comparing digit ratios between children who stutter (CWS) and those who do not stutter (CWNS). Methods A quantitative comparative case–control design was employed, involving 52 children aged 3–12 years, including 26 who stutter and 26 who do not. The lengths of the second and fourth digits of the right hand were measured using a digital Vernier caliper to calculate the 2D:4D ratio. Stuttering severity was evaluated using the Stuttering Severity Instrument–Fourth Edition (SSI-IV). Data were analyzed using SPSS version 27, with descriptive statistics and an independent samples t -test used to compare right-hand 2D:4D digit ratios between the two groups. Results The analysis revealed no statistically significant difference in right-hand 2D:4D digit ratio between children who stutter and those who do not stutter, indicating comparable digit ratios across groups. Effect size analysis showed a small and non-meaningful difference between groups (Cohen's d = −0.24). Post hoc power analysis indicated low statistical power, suggesting caution in interpreting non-significant findings. SSI-IV results showed mild to moderate stuttering severity among affected participants, reflecting clinical heterogeneity within the sample. Conclusion The findings do not support an association between 2D:4D digit ratio and developmental stuttering in this sample. However, due to limited sample size and low statistical power, these results should be interpreted with caution, and further studies with larger samples are recommended to draw more definitive conclusions.