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      Family History Correlates of Digit Ratio Abnormalities in Schizophrenia

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          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).

          Materials and 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.

          Conclusion:

          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.

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          Most cited references28

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          2nd to 4th digit ratios, fetal testosterone and estradiol.

          The ratio of 2nd to 4th digit length (2D:4D) is sexually dimorphic (mean 2D:4D is lower in males than females) and is thought to be fixed early in development. 2D:4D has been reported to be related to fetal growth, hand preference, autism, Asperger's syndrome, sperm counts, family size, age at myocardial infarction in men and breast cancer in women. There is indirect evidence that 2D:4D is established in utero and is negatively related to prenatal testosterone and positively with prenatal estradiol. However, there are no studies which show direct relationships between fetal testosterone (FT), fetal estradiol (FE) and 2D:4D. To investigate the relationships between 2D:4D ratios and FT and FE from amniotic fluid. Cohort study. 33 children. Radioimmunoassays of FT and FE obtained from routine amniocentesis; 2D:4D ratios calculated from 2nd and 4th digit length of the right and left hands at age 2 years. A significant negative association between right 2D:4D ratio and FT/FE ratio, which was independent of sex. These preliminary findings lend support to an association between low 2D:4D and high levels of FT relative to FE, and high 2D:4D with low FT relative to FE.
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            Schizophrenia: genes and environment.

            The historical and genetic foundations of our current understanding of schizophrenia are reviewed, as are the present and future directions for research. Genetic epidemiological investigations, including family, twin, and adoption studies have confirmed the contributions of genetic and environmental determinants of schizophrenia. For example, identical twins show average concordance rates of only 50%; rates of 100% would be expected on the basis of genetic equivalence alone. Genetic factors may cause errors in brain development and synaptic connections. A broad range of environmental components may further damage the brain. Biological components may include pregnancy and delivery complications, such as intrauterine fetal hypoxia, infections, and malnutrition. Primarily nonbiological components may include psychosocial stressors, such as residence in an urban area and dysfunctional family communication. It is likely that the environmental factors interact with the genetic liability in a negative manner to produce disorders in the schizophrenic spectrum. Genetic and environmental components of the disorder are examined, as well as their interactions in producing either neurodevelopmental syndromes or schizophrenia itself. The implication of these findings for prevention and treatment are considered.
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              The use of digit ratios as markers for perinatal androgen action

              Since the ratio of the second-to-fourth finger length was first proposed as a marker for prenatal androgen action in 1998, over 100 studies have been published that have either further tested the association between the digit ratio and prenatal androgens, or employed digit ratios as a marker to investigate the association between prenatal androgens and a variety of outcomes, including behavior, fertility, and disease risks. Despite the clear demand for an adult marker of prenatal androgen action and increased use of digit ratios as such a marker, its validity remains controversial. This review (1) evaluates current evidence for the relationship between digit ratios and prenatal androgens (using experimentation with animal models, amniotic testosterone, and congenital adrenal hyperplasia case-control studies), (2) describes opportunities for future validation tests, and (3) compares the potential advantages and disadvantages of digit ratio measures with more established methods for studying the effects of prenatal androgens.
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                Author and article information

                Journal
                Indian J Psychol Med
                Indian J Psychol Med
                IJPsyM
                Indian Journal of Psychological Medicine
                Medknow Publications & Media Pvt Ltd (India )
                0253-7176
                0975-1564
                Oct-Dec 2012
                : 34
                : 4
                : 355-359
                Affiliations
                [1]Department of Psychiatry and Translational Psychiatry Laboratory, Neurobiology Research Center, National Institute of Mental Health and Neurosciences, Bangalore, Karnataka, India
                Author notes
                Address for correspondence: Dr. Janardhanan C. Narayanaswamy, Department of Psychiatry, Translational Psychiatry Laboratory, Neurobiology Research Center, National Institute of Mental Health asnd Neurosciences (NIMHANS), Bangalore, Karnataka, India. E-mail: jairamnimhans@ 123456gmail.com
                Article
                IJPsyM-34-355
                10.4103/0253-7176.108220
                3662133
                23723544
                a9409a14-f927-43a3-a52a-3a2521e7ef61
                Copyright: © Indian Journal of Psychological Medicine

                This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                Categories
                Original Article

                Clinical Psychology & Psychiatry
                digit ratio,neurodevelopmental,sex differences,schizophrenia
                Clinical Psychology & Psychiatry
                digit ratio, neurodevelopmental, sex differences, schizophrenia

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