Association between tendencies for attention-deficit/hyperactivity disorder (ADHD) and the 2D:4D digit ratio: a cross-cultural replication in Germany and China

The associations between 2D:4D ratio and behavior problems among Chinese preschool children: A cross-sectional study

BACKGROUND

Digit ratio (2D:4D) is considered a biomarker of prenatal androgen activity, the prenatal hormone exposure may affect children's psychology and behavior.

OBJECTIVE

The aim of this study was to analyze the associations between 2D:4D ratio and behavior problems in Chinese preschool children, and to provide ideas for early intervention of children's behavior problems.

METHODS

A total of 548 Chinese preschool children aged 3-6 years were recruited using a stratified cluster sampling method. The Child Behavior Checklist (CBCL) was used to assess the children's behavior. Basic information of the children and their parents was also collected, finger length was directly measured by electronic vernier caliper.

RESULTS

We found that sex and age of the child, mother's educational level, and whether the child was an only child were the influencing factors of behavior problems (P < 0.05). Right-handed 2D:4D was negatively correlated with parent-reported anxiety/depression (P < 0.05), father-reported aggression (P < 0.05) and attention problems (P < 0.01), that is, high levels of testosterone may increase the risk of anxiety and depression, our results were in contrast to previous studies.

CONCLUSION

The 2D:4D ratio may be related to behavior problems among Chinese preschool children, and prenatal testosterone exposure may be an important factor affecting behavior problems.

Lower digit length ratio and aggression in adolescents and young adults with boxer's fracture: A case-control study

Recent evidence shows that a lower second-to-fourth digit ratio (2D:4D), which is a sexually dimorphic trait and the indicator of prenatal testosterone exposure, may be associated with aggressive behaviors. In this cross-sectional, case-control study, we investigated: (1) Are the aggression and impulsivity levels and emotional problems higher? (2) Is the 2D:4D ratio lower in adolescents and young adults who presented with a fifth metacarpal neck fracture (boxer's fracture) compared to controls? (3) Is the digit ratio correlated with aggressive measures in individuals with a fifth metacarpal neck fracture? Seventy-one consecutive patients presented with a fifth metacarpal neck fracture within the age range of 11-25 years old comprised the study group. The control group consisted of 71 age and sex-matched subjects without a history of aggression-related injury. The aggression, impulsiveness, and psychosocial well-being were measured by self-reported questionnaires. 2D:4D was measured by conventional radiography. The 2D:4D ratio was similar between groups, however, when the analyses were conducted separately for sex, females in the study group showed lower 2D:4D than females in the control group (p = 0.001). The aggression level of the study group, measured by the Buss-Perry Aggression Questionnaire was higher than the control group (p = 0.014). The impulsiveness scores on the Barratt Impulsiveness Scale-11 were similar (p = 0.60) and the total difficulty score on the Strengths and Difficulties Questionnaire was higher in the study group (p = 0.009). A lower 2D:4D ratio significantly predicted verbal and total aggression scores (p = 0.036, p = 0.032, respectively). Our findings suggest that females with a history of aggression-related injury have lower 2D:4D, and a lower 2D:4D is correlated with higher aggression levels in both sexes. Understanding and addressing aggression in these patients may help prevent further self-inflicted injuries.

Investigating the correlation between 2D:4D finger digit ratios and attention gathering skills of 60-72 month-old children

BACKGROUND

Digit ratio 2D:4D is used to follow children's development process and examine behaviours and abilities.

AIM

The aim of this study is to determine the correlation between the 2D:4D digit ratios of 60-72 month-old children and their attention gathering skills, as well as whether the 2D:4D digit ratio and attention gathering skills of children differ based on independent variables.

METHOD

The sample of the study, designed in the correlational survey model, consisted of a total of 112 children aged 60-72 months who were attending preschool education in Malatya province in Turkey. The data were analysed using SPSS packaged software.

RESULTS

It was determined that there was a positive low significant correlation between attention gathering skills and the right hand 2D:4D digit ratio in 60-72 month-old children. In addition to, no significant difference was found between the children's FTF-K scores and the right hand 2D:4D digit ratio in terms of the variable of mother's status of exercising, but there was a significant difference between their FTF-K scores and the left hand 2D:4D digit ratio in terms of the variable of the mother's status of exercising.

CONCLUSIONS

The findings of the study demonstrate the importance of the study for revealing clues about children's attention gathering/concentration levels from their early periods, and promoting their attention gathering skills and generally their cognitive development.

Maternal polycystic ovary syndrome and attention deficit hyperactivity disorder in offspring at 3 years of age: Odense Child Cohort

INTRODUCTION

Previous data suggested a link between maternal polycystic ovary syndrome (PCOS) and offspring attention deficit hyperactivity disorder (ADHD), which could be mediated by higher prenatal androgen exposure.

MATERIAL AND METHODS

The study was part of the prospective Odense Child Cohort and included 1776 pregnant women, 165 (9%) with PCOS and 1607 (91%) controls. ADHD symptoms at 3 years of age were defined using the parent-reported questionnaire Child Behavior Checklist/1.5-5 (scores >90th centile of Danish national standard). Maternal blood samples were collected in the third trimester measuring total testosterone by mass spectrometry, sex hormone-binding globulin, and calculated free testosterone. Offspring anogenital distance was measured at 3 months of age. Regression models were performed with presence of ADHD symptoms as the dependent variable and adjusted for maternal age, body mass index, parity, smoking status, educational level, and parental psychiatric diagnoses.

RESULTS

ADHD symptoms were present in 105/937 (11%) boys and 72/839 (9%) girls. In boys, maternal PCOS was positively associated with ADHD symptoms (unadjusted odds ratio [OR] 1.91, 95% CI 1.07-3.43, p = 0.03, adjusted OR 2.20, 95% CI 1.20-4.02, p = 0.01), whereas maternal PCOS was not associated with ADHD symptoms in girls. Maternal total testosterone, free testosterone, and offspring anogenital distance were not associated with higher risk of ADHD symptoms in the offspring.

CONCLUSIONS

Higher risk of ADHD in boys born of mothers with PCOS were not associated with maternal third-trimester testosterone levels or offspring anogenital distance.

Digit ratio (2D:4D) and handedness: A meta-analysis of the available literature

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.

Fluctuating asymmetry of finger lengths, digit ratio (2D:4D), and tattoos: A pre-registered replication and extension of Koziel et al. (2010)

BACKGROUND

Tattoos bring risks yet no obvious evolutionary benefit. Koziel et al. (2010) reported increased fluctuating symmetry (a proxy for low developmental instability) in tattooed men, suggesting they could serve as fitness indicators.

AIMS

We replicate and extend the findings of Koziel et al. by examining fluctuating asymmetry of finger lengths and digit ratio (2D:4D) (a putative indicator of prenatal testosterone exposure) as predictors of adult tattoo prevalence.

STUDY DESIGN

We used an online survey with a correlational design.

SUBJECTS

Participants were recruited from the UK and Poland via university participant pools and social media. Data were available for presence/absence of tattoos and at least one predictor variable (composite Fluctuating Asymmetry [cFA], right-hand digit ratio [R2D:4D] and left-hand digit ratio [L2D:4D]) for n = 186 males and n = 997 females.

OUTCOME MEASURES

We firstly assessed presence/absence of tattoos; when at least one tattoo was present, we also examined overall number and highest visibility.

RESULTS

Greater cFA was associated with lower likelihood of having tattoos in males, though in females greater cFA was associated with higher numbers of tattoos. R2D:4D and L2D:4D correlated negatively with number of tattoos in males, and a positive correlation between L2D:4D and number of tattoos was observed in females. However, these latter findings did not remain significant after controlling for covariates.

CONCLUSIONS

Tattoos may act as fitness indicators in males, though this explanation appears not to extend to females. Prenatal testosterone may also play a role, though doubt is cast on this premise because 2D:4D effects did not remain statistically significant after controlling for covariates.

Blood oxytocin levels are not associated with ADHD tendencies and emotionality in healthy adults

Oxytocin (OT) regulates social and emotional behaviour. Core symptoms of attention-deficit/hyperactivity disorder (ADHD) include social and emotional dysfunctions potentially associated with lower endogenous OT levels. A dimensional approach was employed to examine relationships between plasma OT levels, ADHD tendencies, and emotionality in a healthy adult sample. Moreover, we aimed at replication of results regarding ADHD tendencies and emotionality from our previous work. Subjects were N = 110 healthy Chinese males (M_age: 22.01 ± 2.02 years). Variables of interest were plasma OT levels, individual variations in ADHD tendencies assessed via the Adult ADHD Self-Report Scale Symptom Checklist (ASRS), and positive and negative emotionality assessed via primary emotional traits of the Affective Neuroscience Personality Scales (ANPS). Hypotheses were tested by means of (partial) Spearman and Pearson correlations. Plasma OT levels were neither related to ADHD tendencies, nor to primary emotional traits. ADHD tendencies were significantly related to higher negative emotionality (correlation coefficients: r= .35 to r = .47) and lower positive emotionality (correlation coefficients: r= -.42 to r = -.36). The absence of associations between plasma OT levels and ADHD tendencies, primary emotional traits, and emotionality might be explained by the lack of robust associations between peripheral and central OT levels. Results regarding ADHD tendencies and emotionality replicate previous findings, emphasizing that (sub-clinically) elevated ADHD tendencies associate with dysregulated emotionality. Future studies examining the role of endogenous OT in ADHD should explore the generalizability of the present findings to women and patients with ADHD.