Identifying women at risk for stress and depression using the 2D:4D digit ratio

Introduction: Depression, anxiety, and stress are common mental health problems, and often comprise a significant socioeconomic burden to both patient and society [1]. The 2D:4D digit ratio has been proposed as a potential biomarker for these syndromes. The 2D:4D digit ratio is the ratio in length between the 2nd (index) and 4th (ring) finger. The 2D:4D ratio is a sexually dimorphic trait, known to depend on the amount of prenatal sex hormones [2]. Low 2D:4D ratios are associated with high levels of fetal testosterone in relation to fetal estrogen and vice versa [3]. Prenatal sex hormones influence both digit growth and the development of the central nervous system (CNS). Thus, prenatal sex hormones may have an impact on later life CNS functioning. For example, in men, a higher 2D:4D ratio has been associated with increased risk of having depression [4]. Therefore, it has been hypothesized that the 2D:4D digit ratio can serve as a biomarker for CNS disorders. Aim of the study: To determine whether the 2D:4D digit ratio is a suitable biomarker to screen subjects for increased risk for depression, anxiety, and stress. Methods: Participants were recruited among students of Utrecht University, The Netherlands. They completed the Depression, Anxiety and Stress Scale -21 (DASS-21) [5], the short 21- item version of the original DASS. The DASS-21 measures distress on three subscales: (1) depression and (2) anxiety (symptoms of psychological arousal), and (3) stress (cognitive, subjective symptoms of anxiety). The 21 items can be endorsed on a zero to three point Likert scale to indicate to what extent they apply to them. For both hands, digit lengths of the second (2D, index finger) and fourth (4D, ring finger) finger were measured using digital Vernier calipers recording to 0.01 mm, and the 2D:4D digit ratio was computed. Scores on the DASS-21 subscales were correlated with 2D:4D digit ratios (nonparametric Spearman's r). The analyses were conducted overall, and for men and women separately. Results: N= 271 subjects (N = 147 women and N= 124 men) participated in the study. Their mean (SD) age was 20.7 (2.3) years old. The left hand 2D:4D digit ratio correlated significantly with the overall DASS-21 score (r = -0.134, p = 0.029) and the subscale of depression (r = -0.166, p = 0.0069), but not with anxiety and stress. No significant correlations were found with the right hand 2D:4D. In women, the left hand 2D:4D digit ratio correlated significantly with the overall DASS-21 score (r = -0.261, p = 0.002) and the subscales of depression (r = -0.230, p = 0.005) and stress (r = -0.241, p = 0.004). In men, none of the correlations was significant. Also, for the right hand 2D:4D no significant correlations were observed with DASS-21 outcome measures. Conclusions: Significant correlations were found between the left hand 2D:4D digit ratio and scores of depression and stress in women, but not in men. More research is needed to elucidate the rationale for these observed gender differences.