title: Family history correlates of digit ratio abnormalities in schizophrenia.
abstract: BACKGROUND
  The differences in digit ratio are proposed to arise due to differential effects of sex steroids on the growth of finger bones. In this study, we sought to examine the sex differences and the influence of family history of psychosis on digit ratio in patients with schizophrenia compared to matched healthy controls (HCs).
  
  
  METHODS
  Digit ratio (2D: 4D) was examined for a large sample of schizophrenia patients (n=200) and HC (n=177) to evaluate the potential effects of family history.
  
  
  RESULTS
  The right hand 2D: 4D digit ratio was lesser in schizophrenia patients compared to HC (0.97±0.05 vs 0.98±0.04, t=2.2, P=0.02). There was a significant difference in the right hand 2D: 4D digit ratio of female patients with schizophrenia when compared to female HCs (0.96±0.05 vs 0.98±0.03, t=2.1, P=0.03) while males showed no such difference on either hands. On the contrary, family history‑positive males showed a significantly greater digit ratio for the left hand (FH present (0.99±0.04) vs HC (0.97±0.04), t=2.15, P=0.03), while there was no difference between family history‑positive females and HC.
  
  
  CONCLUSIONS
  Overall, in patients, reversal of expected "directionality" in digit ratio was observed in our study with greater left 2D: 4D in male patients having a family history of schizophrenia being a novel finding. Reversal of sexual dimorphism has been linked to the pathogenesis of schizophrenia. It is possible that such reversal might have a putative genetic basis, perhaps only in men with schizophrenia.
authors.affiliation: Department of Psychiatry and Translational Psychiatry Laboratory, Neurobiology Research Center, National Institute of Mental Health and Neurosciences, Bangalore, Karnataka, India.
authors.forename: Anjith
authors.initials: A
authors.lastname: Divakaran
authors.forename: Janardhanan C
authors.initials: JC
authors.lastname: Narayanaswamy
authors.forename: Sunil V
authors.initials: SV
authors.lastname: Kalmady
authors.forename: Vidya
authors.initials: V
authors.lastname: Narayan
authors.forename: Naren P
authors.initials: NP
authors.lastname: Rao
authors.forename: Ganesan
authors.initials: G
authors.lastname: Venkatasubramanian
keywords: Digit ratio; neurodevelopmental; schizophrenia; sex differences