Second to fourth finger ratio and possible precursors of developmental psychopathology in preschool children

Background: The influence of sex steroids upon brain development has been suggested to mediate sex differences in developmental psychopathology. The ratio of the length of index finger or second finger to the ring finger or fourth finger (the 2D:4D ratio) appears to be a marker of early sex hormone exposure, with low 2D:4D associated with high prenatal testosterone and high 2D:4D associated with high prenatal oestrogen. This relationship allows a non-invasive measure of the long-term influence of prenatal sex steroids. Behaviours such as hyperactivity and poor social cognition are common in preschoolers. An association between 2D:4D and these possible precursors of psychopathology would be most readily identified in this group. Aim: To identify relationships between 2D:4D ratio and behaviours in preschool children which constitute possible precursors of developmental psychopathology. Study design: Population survey. Method: The 2D:4D ratio was measured in a group of preschool children and behavioural questionnaires were given to parents and teachers. Results: Sex differences in behaviours were small, whilst correlations with 2D:4D were strong. Low 2D:4D was related to hyperactivity and poor social cognitive function in girls, and high 2D:4D with emotional symptoms in boys. Conclusions: We suggest that during early brain development androgens increase the probability of hyperactivity and poor social cognition in girls. Early oestrogens increase the probability of emotional problems in boys. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.