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Eichler A, Kaufmann F, Titzmann A, Fasching PA, Beckmann MW, Gerlach J, Kratz O, Moll GH, Buchholz VN, Kornhuber J, Lenz B. 2D:4D biomarker reliability and validity in a within-subject pregnancy-childhood-adolescence cohort. Early Hum Dev 2023; 181:105776. [PMID: 37084692 DOI: 10.1016/j.earlhumdev.2023.105776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 04/11/2023] [Accepted: 04/11/2023] [Indexed: 04/23/2023]
Abstract
BACKGROUND A lot of studies use the second-to-fourth digit length ratio (2D:4D) as a biomarker for intrauterine androgen load to predict behavioral and mental health problems. Thus, knowledge of 2D:4D's metric properties, namely reliability and validity, is essential. METHOD 2D:4D handscans were available from 149 adolescents (M = 13.32 years, SD = 0.35) and their mothers. For 88 adolescents, there were also primary-school age handscans (M = 7.87 years, SD = 0.68). Prenatal risks for the 1st to 3rd trimesters were recorded during the 3rd trimester of pregnancy (alcohol exposition: meconium biomarker and maternal self-report; nicotine exposition: maternal self-report; maternal depressive symptoms and subjective stress: questionnaires). RESULTS The 2D:4D ratio was highly stable from childhood to early adolescence. However, both developmental and sex effects were present: The 2D:4D ratio increased with age and was higher in adolescent girls vs. boys. Significant 2D:4D mother-child associations were found for girls. Significant main effects could be found for the prenatal risk factors alcohol (self-report) and nicotine consumption. CONCLUSION In line with earlier studies, the 2D:4D biomarker proved to be an inter-individually stable measure with an intra-individual increase from childhood to early adolescence. Sex differences in adolescence and associations with maternal prenatal health behaviour underline the validity of the biomarker. Findings on heritability emphasize the importance of interpreting 2D:4D results in a sex-specific manner.
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Affiliation(s)
- Anna Eichler
- Department of Child and Adolescent Mental Health, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Franziska Kaufmann
- Department of Child and Adolescent Mental Health, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Adriana Titzmann
- Department of Obstetrics and Gynecology, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Peter A Fasching
- Department of Obstetrics and Gynecology, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Matthias W Beckmann
- Department of Obstetrics and Gynecology, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Jennifer Gerlach
- Department of Child and Adolescent Mental Health, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Oliver Kratz
- Department of Child and Adolescent Mental Health, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Gunther H Moll
- Department of Child and Adolescent Mental Health, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Verena N Buchholz
- Department of Psychiatry and Psychotherapy, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Johannes Kornhuber
- Department of Psychiatry and Psychotherapy, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Bernd Lenz
- Department of Psychiatry and Psychotherapy, University Hospital Erlangen, Friedrich-Alexander-Univesität Erlangen-Nürnberg (FAU), Erlangen, Germany; Department of Addictive Behavior and Addiction Medicine, Central Institute of Mental Health (CIMH), Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
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2
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Finley B, Kalwij A, Kapteyn A. Born to be wild: Second-to-fourth digit length ratio and risk preferences. ECONOMICS AND HUMAN BIOLOGY 2022; 47:101178. [PMID: 36084390 DOI: 10.1016/j.ehb.2022.101178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 07/20/2022] [Accepted: 08/22/2022] [Indexed: 06/15/2023]
Abstract
The second-to-fourth digit length ratio of an individual's hand (digit ratio) is a putative biomarker for prenatal exposure to testosterone. We examine the hypothesized negative association between the digit ratio and the preference for risk taking within a large U.S. population survey. Our statistical framework provides a cardinal proxy for the true digit ratio based on ordinal digit ratio measurements and accounts for measurement error under the assumptions of Gaussianity and time-invariant true digit ratios. Our empirical findings support the hypothesis and suggest a meaningful biological basis for risk preferences.
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Affiliation(s)
| | - Adriaan Kalwij
- Utrecht University School of Economics, The Netherlands.
| | - Arie Kapteyn
- Center for Economic and Social Research at the University of Southern California, United States.
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3
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Alex AM, Ruvio T, Xia K, Jha SC, Girault JB, Wang L, Li G, Shen D, Cornea E, Styner MA, Gilmore JH, Knickmeyer RC. Influence of gonadal steroids on cortical surface area in infancy. Cereb Cortex 2022; 32:3206-3223. [PMID: 34952542 PMCID: PMC9340392 DOI: 10.1093/cercor/bhab410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 09/13/2021] [Accepted: 09/14/2021] [Indexed: 12/27/2022] Open
Abstract
Sex differences in the human brain emerge as early as mid-gestation and have been linked to sex hormones, particularly testosterone. Here, we analyzed the influence of markers of early sex hormone exposure (polygenic risk score (PRS) for testosterone, salivary testosterone, number of CAG repeats, digit ratios, and PRS for estradiol) on the growth pattern of cortical surface area in a longitudinal cohort of 722 infants. We found PRS for testosterone and right-hand digit ratio to be significantly associated with surface area, but only in females. PRS for testosterone at the most stringent P value threshold was positively associated with surface area development over time. Higher right-hand digit ratio, which is indicative of low prenatal testosterone levels, was negatively related to surface area in females. The current work suggests that variation in testosterone levels during both the prenatal and postnatal period may contribute to cortical surface area development in female infants.
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Affiliation(s)
- Ann Mary Alex
- Neuroengineering Division, Institute for Quantitative Health Sciences and Engineering, Michigan State University, East Lansing, MI 48824, USA
| | - Tom Ruvio
- Neuroengineering Division, Institute for Quantitative Health Sciences and Engineering, Michigan State University, East Lansing, MI 48824, USA
| | - Kai Xia
- Department of Psychiatry, University of North Carolina Chapel Hill, Chapel Hill, NC 27599, USA
| | - Shaili C Jha
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Jessica B Girault
- Department of Psychiatry, University of North Carolina Chapel Hill, Chapel Hill, NC 27599, USA
- Carolina Institute for Developmental Disabilities, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Li Wang
- Department of Radiology and Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Gang Li
- Department of Radiology and Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Dinggang Shen
- School of Biomedical Engineering, ShanghaiTech University, Shanghai 201210, China
- Department of Artificial Intelligence, Korea University, Seoul 02841, Republic of Korea
| | - Emil Cornea
- Department of Psychiatry, University of North Carolina Chapel Hill, Chapel Hill, NC 27599, USA
| | - Martin A Styner
- Department of Psychiatry, University of North Carolina Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Computer Science, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - John H Gilmore
- Department of Psychiatry, University of North Carolina Chapel Hill, Chapel Hill, NC 27599, USA
| | - Rebecca C Knickmeyer
- Address correspondence to Rebecca C. Knickmeyer, Institute for Quantitative Health Science and Engineering, 775 Woodlot Dr, East Lansing, MI 48824, USA.
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4
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Second to fourth (2D:4D) digit ratio and their relationships among a mother and child population in Ghana. Sci Rep 2021; 11:13028. [PMID: 34158576 PMCID: PMC8219683 DOI: 10.1038/s41598-021-92358-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 06/07/2021] [Indexed: 11/12/2022] Open
Abstract
The study aimed to determine the relationship between digit ratios among a mother–child population in Ghana. This was a cross-sectional study from December 2020 to April 2021 involving 272 mothers, their daughters (n = 132) and their sons (n = 140). The right (2D:4DR) and the left (2D:4DL) digit ratios were measured using computer-assisted analysis. The data were analysed in SPSS (v23) and GraphPad Prism (v8) at an alpha value of 0.05. The mean ± SD age of the mothers was 23.9 ± 3.67 years while the median (IQR) age of daughters was 116(54–240) days and sons, 134(54–240) days. The mean ± SD 2D:4DR were 0.94 ± 0.04, 0.91 ± 0.04 and 0.90 ± 0.04 respectively for mothers, daughters and sons. The mean ± SD 2D:4DL was 0.93 ± 0.04, for mothers, 0.92 ± 0.05 for daughters and 0.92 ± 0.05 for sons. The daughters and sons showed leftward asymmetry while the mothers showed rightward asymmetry in digit ratios. The 2D:4DR of sons was significantly lower than daughters (P = 0.031). There were negative correlations between the 2D:4DL and age of daughters (r = −0.182, P = 0.043) and sons (r = −0.221, P = 0.012). The 2D:4DR of mothers was positively correlated with that of daughters (r = 0.332, P = 0.000) and that of sons (r = 0.233, P = 0.008). There are significant relationships between digit ratios in a mother–child population.
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Butovskaya M, Burkova V, Apalkova Y, Dronova D, Rostovtseva V, Karelin D, Mkrtchyan R, Negasheva M, Batsevich V. Sex, population origin, age and average digit length as predictors of digit ratio in three large world populations. Sci Rep 2021; 11:8157. [PMID: 33854119 PMCID: PMC8046776 DOI: 10.1038/s41598-021-87394-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 03/25/2021] [Indexed: 02/06/2023] Open
Abstract
Recently, a number of authors have claimed that sexual dimorphism in the second-to-fourth digit ratio (2D:4D) is simply dependent on digit length and is an artifact of allometry. The goal of our study is to verify the validity of these assumptions. The study sample comprised 7,582 individuals (3,802 men and 3,780 women) from three large world populations: Europeans (n = 3043), East Africans (n = 2844), and Central Asians (n = 1695). The lengths of the second and fourth digits on both hands were measured. Digit ratios were computed according to standard procedures. Analyses were conducted separately for each hand for the whole sample and in succession for the three large populations. Additionally, we separately tested four age cohorts (≤ 13, 14-18, 19-30, and 31 ≥ years) to test the effect of developmental allometry. The second and fourth digits showed strong positive linear relationships on both hands, and demonstrated an increase with age; digit length in women from the youngest age cohort was longer or equal to that of men, and shorter than men in older age cohorts. However, the 2D:4D magnitude and its sexual dimorphism remained stable throughout the ontogeny. To test for an allometric effect on 2D:4D, the average digit lengths were calculated. Both sex and population origin were permanent reliable predictors of 2D:4D, whereas average digit length was not. Height was applied as another measure of allometric effect on the limited sample (≤ 30 years) from the European population, along with sex and age. No allometric effect was observed in this case. We conclude that sex differences in 2D:4D are not an artifact of allometry.
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Affiliation(s)
- Marina Butovskaya
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninsky pr., 32a, Moscow, Russia, 119991.
- National Research University Higher School of Economics, Moscow, Russia.
- Russian State University for the Humanities, Moscow, Russia.
| | - Valentina Burkova
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninsky pr., 32a, Moscow, Russia, 119991
- National Research University Higher School of Economics, Moscow, Russia
| | - Yulia Apalkova
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninsky pr., 32a, Moscow, Russia, 119991
| | - Daria Dronova
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninsky pr., 32a, Moscow, Russia, 119991
| | - Victoria Rostovtseva
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninsky pr., 32a, Moscow, Russia, 119991
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Rodríguez-Ramos Á, Moriana JA, García-Torres F, Ruiz-Rubio M. Emotional stability is related to 2D:4D and social desirability in women: Possible implications on subjective well-being and psychopathology. PLoS One 2021; 16:e0248368. [PMID: 33690629 PMCID: PMC7942991 DOI: 10.1371/journal.pone.0248368] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 02/23/2021] [Indexed: 01/07/2023] Open
Abstract
Emotional stability-Neuroticism is a complex construct influenced by genetics and environmental factors. Women tend to exhibit higher neuroticism scores than men, which may be associated with an increased risk of suffering from some common mental conditions. Some authors have pointed out the influence of sex hormones, since they induce sexual differentiation of the brain that can lead to sex-specific behaviors. 2D:4D digit ratio is commonly used as a marker of prenatal sex hormones. In this study we analyzed whether there was an association between 2D:4D and personality measured through the BFQ in a homogeneous sample of 101 young women college students. We found a positive association between 2D:4D and emotional stability, as well as with its subdimensions emotion control and impulse control. This association could be quadratic and nonlinear. However, no association was found with the other four dimensions. We also measured anxiety, depression and global life satisfaction, variables related to neuroticism. We observed that emotional stability is positively associated to social desirability and global life satisfaction, and negatively related to anxiety and depression. On the other hand, we did not find any association between 2D:4D and anxiety, depression, and global life satisfaction. These results can be linked to other aspects such as subjective well-being and psychopathological symptoms. This study may help to better understand how these constructs are related and could lead to future projects to elucidated how these variables influence personality.
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Affiliation(s)
- Ángel Rodríguez-Ramos
- Department of Genetics, University of Córdoba, Córdoba, Spain
- Department of Psychology, University of Córdoba, Córdoba, Spain
- Maimónides Biomedical Research Institute of Córdoba (IMIBIC), Córdoba, Spain
- University Hospital Reina Sofía of Córdoba, Córdoba, Spain
| | - Juan Antonio Moriana
- Department of Psychology, University of Córdoba, Córdoba, Spain
- Maimónides Biomedical Research Institute of Córdoba (IMIBIC), Córdoba, Spain
- University Hospital Reina Sofía of Córdoba, Córdoba, Spain
| | - Francisco García-Torres
- Department of Psychology, University of Córdoba, Córdoba, Spain
- Maimónides Biomedical Research Institute of Córdoba (IMIBIC), Córdoba, Spain
- University Hospital Reina Sofía of Córdoba, Córdoba, Spain
| | - Manuel Ruiz-Rubio
- Department of Genetics, University of Córdoba, Córdoba, Spain
- Maimónides Biomedical Research Institute of Córdoba (IMIBIC), Córdoba, Spain
- University Hospital Reina Sofía of Córdoba, Córdoba, Spain
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7
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Richards G, Medland SE, Beaton AA. Digit ratio (2D:4D) and handedness: A meta-analysis of the available literature. Laterality 2021; 26:421-484. [PMID: 33517845 DOI: 10.1080/1357650x.2020.1862141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The Geschwind-Behan-Galaburda and sexual differentiation models predict an association between elevated foetal androgen exposure and left-handedness whereas the callosal hypothesis predicts the opposite. We present a meta-analysis of correlations between handedness and digit ratio (2D:4D), a putative marker of prenatal testosterone. Left-handedness predicted low (male-typical) right-hand digit ratio (R2D:4D), high (female-typical) left-hand digit ratio (L2D:4D), and low R2D:4D-L2D:4D directional asymmetry (D[R-L]). Effect sizes were extremely small and not moderated by sex or method of measuring handedness or 2D:4D. The same general pattern was observed after excluding the very large study (110,329 males, 90,412 females) of Manning and Peters ([2009]. Digit ratio (2D:4D) and hand preference for writing in the BBC Internet Study. Laterality: Asymmetries of Body, Brain and Cognition, 14(5), 528-540. doi:10.1080/13576500802637872); however, no significant effects for R2D:4D were observed once these samples were removed. The results do not confirm any theory linking prenatal androgens with handedness, so we speculate they instead reflect the mechanical action of writing causing subtle changes in the musculature and/or fat pads of the fingers. Gripping a pen/pencil might cause an increase in 2D relative to 4D (and/or decrease in 4D relative to 2D) resulting in higher ratios on the writing-hand; furthermore, this could differ between left- and right-handers due to writing in the left-to-right direction (as in English) having asymmetrical effects depending on which hand is used.
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Affiliation(s)
- Gareth Richards
- School of Psychology, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK.,Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, UK.,Centre for Research on Play in Education, Development & Learning, Faculty of Education, University of Cambridge, Cambridge, UK
| | - Sarah E Medland
- Psychiatric Genetics, QIMR Berghofer Medical Research Institute, Brisbane, Australia.,School of Psychology, University of Queensland, St Lucia, Australia.,School of Psychology and Counselling, Queensland University of Technology, Brisbane, Australia
| | - Alan A Beaton
- Department of Psychology, School of Human & Health Sciences, Swansea University, Swansea, UK.,Department of Psychology, Aberystwyth University, Aberystwyth, UK
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Richards G, Baron-Cohen S, van Steen T, Galvin J. Assortative mating and digit ratio (2D:4D): A pre-registered empirical study and meta-analysis. Early Hum Dev 2020; 151:105159. [PMID: 32942249 DOI: 10.1016/j.earlhumdev.2020.105159] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 08/10/2020] [Accepted: 08/18/2020] [Indexed: 02/06/2023]
Abstract
BACKGROUND It has been hypothesised that the ratio of length between the second and fourth fingers (2D:4D), commonly employed as an indicator of foetal sex hormone exposure, may be positively correlated between heterosexual partners. AIMS As previous evidence has been conflicting, our study aimed to determine whether intra-couple correlations exist for digit ratio variables, and if so, to estimate the size and direction of these effects. STUDY DESIGN We present a preregistered (osf.io/6jg8p) correlational study and quantitative meta-analysis of the available literature, and attempted to locate further published and unpublished data (i.e. 'grey literature') by contacting n = 248 researchers in the 2D:4D and related fields. SUBJECTS n = 58 heterosexual dating couples from the UK took part in our empirical study, and the meta-analysis included data from k = 11 samples. OUTCOME MEASURES We measured digit ratio for the right hand (R2D:4D), left hand (L2D:4D), and average of both hands (M2D:4D), as well as the right-left-difference (D[R-L]). RESULTS We found no evidence of significant positive intra-couple correlations in our own data, but a significant (positive) meta-analytic effect size estimate emerged for R2D:4D (r = 0.072, p = 0.014). The meta-analytic effects for L2D:4D (r = 0.043, p = 0.303), M2D:4D (r = 0.070, p = 0.225), and D[R-L] (r = 0.028, p = 0.649) were all in the same direction but not statistically significant. However, if the sample from Klimek et al. (2014, 2016) were omitted, meta-analysis would also yield a significant positive correlation for M2D:4D (r = 0.128, p = 0.001). CONCLUSIONS Although our findings are based on a fairly small range of studies, which themselves provide a relatively small sample of participants, they do imply the intriguing possibility of small effects of positive assortment in relation to characteristics associated with the prenatal hormonal environment.
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Affiliation(s)
- Gareth Richards
- School of Psychology, Faculty of Medical Sciences, Newcastle University, UK; Autism Research Centre, Department of Psychiatry, University of Cambridge, UK.
| | - Simon Baron-Cohen
- Autism Research Centre, Department of Psychiatry, University of Cambridge, UK
| | - Tommy van Steen
- Institute of Security and Global Affairs, Universiteit Leiden, Netherlands
| | - John Galvin
- Department of Psychology, Birmingham City University, UK
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Richards G, Browne WV, Aydin E, Constantinescu M, Nave G, Kim MS, Watson SJ. Digit ratio (2D:4D) and congenital adrenal hyperplasia (CAH): Systematic literature review and meta-analysis. Horm Behav 2020; 126:104867. [PMID: 32998030 DOI: 10.1016/j.yhbeh.2020.104867] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 09/18/2020] [Accepted: 09/19/2020] [Indexed: 01/15/2023]
Abstract
The ratio of length between the second and fourth fingers (2D:4D) is commonly used as an indicator of prenatal sex hormone exposure. Several approaches have been used to try to validate the measure, including examining 2D:4D in people with congenital adrenal hyperplasia (CAH), a suite of conditions characterised by elevated adrenal androgen production secondary to defective steroidogenesis. We present a systematic review and meta-analysis that examines the relationship between these two variables. Twelve articles relating to nine CAH cohorts were identified, and 2D:4D comparisons have been made between cases and controls in eight of these cohorts. Altogether, at least one 2D:4D variable has been compared between n = 251 females with CAH and n = 358 unaffected females, and between n = 108 males with CAH and n = 204 unaffected males. A previous meta-analysis (Hönekopp and Watson, 2010) reported lower right hand (R2D:4D) and left hand (L2D:4D) digit ratios in patients with CAH relative to sex-matched controls. Our meta-analysis showed the same pattern, with medium effect sizes for R2D:4D and small effect sizes for L2D:4D. Differences of small magnitude were also observed for M2D:4D, and no significant effects were observed for D[R-L]. Notably, the only effects that remained statistically significant when stratified by sex were R2D:4D in males and L2D:4D in females, and the average effect size had reduced by 46.70% since the meta-analysis of Hönekopp and Watson (2010). We also found that individual comparisons in this literature were considerably underpowered, and that patterns of sexual dimorphism in 2D:4D were similar in CAH samples as in typically developing populations. Findings are discussed in relation to the prenatal androgen hypothesis as well as alternative explanations.
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Affiliation(s)
- Gareth Richards
- School of Psychology, Faculty of Medical Sciences, Newcastle University, UK; Autism Research Centre, Department of Psychiatry, University of Cambridge, UK.
| | | | - Ezra Aydin
- Autism Research Centre, Department of Psychiatry, University of Cambridge, UK
| | - Mihaela Constantinescu
- Gender Development Research Centre, University of Cambridge, UK; School of Psychology, University of East London, UK
| | - Gideon Nave
- Marketing Department, The Wharton School, University of Pennsylvania, USA
| | - Mimi S Kim
- Keck School of Medicine, University of Southern California, USA
| | - Steven J Watson
- School of Psychology, Faculty of Medical Sciences, Newcastle University, UK; Department of Psychology of Conflict, Risk and Safety, University of Twente, Netherlands
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Zhang K, Yang X, Zhang M, Wang C, Fang P, Xue M, Zhao J, Gao X, Pan R, Gong P. Revisiting the relationships of 2D:4D with androgen receptor (AR) gene and current testosterone levels: Replication study and meta-analyses. J Neurosci Res 2019; 98:353-370. [PMID: 31359506 DOI: 10.1002/jnr.24502] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 07/13/2019] [Accepted: 07/15/2019] [Indexed: 01/07/2023]
Abstract
The relationships of digit ratio (2D:4D) with the length of AR (CAG)n, and testosterone levels from saliva and blood have been extensively debated over the years. This research including three studies further clarifies such controversies. To do so, we re-examined the relationships between the length of AR (CAG)n, 2D:4D, and current testosterone levels, through replication study and meta-analysis for each study. The results indicate: (a) the length of AR (CAG)n is not significantly associated with 2D:4D; (b) current testosterone levels are not significantly associated with the ratio; and (c) the length is not significantly associated with testosterone levels. Thus, AR (CAG)n and current testosterone levels are not significantly related to 2D:4D at individual level.
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Affiliation(s)
- Kejin Zhang
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an, China.,College of Life Science, Northwest University, Xi'an, China
| | - Xing Yang
- College of Life Science, Northwest University, Xi'an, China
| | - Mengfei Zhang
- College of Life Science, Northwest University, Xi'an, China
| | - Chunlan Wang
- College of Life Science, Northwest University, Xi'an, China
| | - Pengpeng Fang
- College of Life Science, Northwest University, Xi'an, China
| | - Mengying Xue
- College of Life Science, Northwest University, Xi'an, China
| | - Jing Zhao
- College of Life Science, Northwest University, Xi'an, China
| | - Xiaocai Gao
- Institute of Population and Health, Northwest University, Xi'an, China
| | - Ruliang Pan
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an, China.,School of Human Sciences, Centre for Evolutionary Biology, The University of Western Australia, Perth, WA, Australia.,School of Biological Sciences, The University of Western Australia, Perth, WA, Australia
| | - Pingyuan Gong
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an, China.,College of Life Science, Northwest University, Xi'an, China.,Institute of Population and Health, Northwest University, Xi'an, China.,Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, China
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