9/25/2023 0 Comments Higher 2d 4d ratio womenUntil recently, the evidence linking the 2D:4D ratio to prenatal androgen exposure has been either correlational or indirect. Because the gender difference may not be as strong as previously claimed, we examined this in the context of our cohort study of Chinese children. However, at least one study ( Knickmeyer et al., 2011) that failed to observe a gender difference had a relatively large sample size ( N = 374). Therefore, researchers have partly attributed these anomalous findings in children and adults to be due to the study’s small sample size. Although most of the studies that did not detect a gender difference had relatively balanced male to female gender ratios (0.91–1.07), their sample sizes were small ( N = 56–165). Furthermore, several adult studies have failed to observe this gender difference ( Austin, Manning, McInroy, & Mathews, 2002 Benderlioglu & Nelson, 2004). Many studies have reported sex differences in digit ratios, but at least two studies have failed to observe this effect in children and infants ( Fink, Manning, Williams, & Podmore-Nappin, 2007 Knickmeyer, Woolson, Hamer, Konneker, & Gilmore, 2011). That 2D:4D ratios are also relatively little affected by puberty and increase only slightly during childhood ( McIntyre, Ellison, Lieberman, Demerath, & Towne, 2005 Trivers, Manning, & Jacobson, 2006) has resulted in this ratio being proposed as a viable biological marker of early developmental processes ( Manning et al., 1998). A study of aborted human fetuses has argued that fetal 2D:4D ratios do not change with gestational age and sex differences in 2D:4D ratios are already present by the end of the first trimester of fetal development ( Malas, Dogan, Evcil, & Desdicioglu, 2006). On average, this ratio is lower for males than it is for females ( Manning et al., 1998 Vermeersch, T’Sjoen, Kaufman, & Vincke, 2008), a finding that has been replicated in several geographic locations ( Manning, Stewart, Bundred, & Trivers, 2004). In humans, the 2D:4D ratio has long been recognized as a sexually dimorphic trait ( George, 1930) and has more recently been associated with prenatal testosterone exposure ( Manning, Scott, Wilson, & Lewis-Jones, 1998). In this study we extend prior work on prenatal risk factors for externalizing behavior problems by further examining this indirect marker for prenatal androgen exposure in a community sample of male and female schoolchildren, extending research from Western cultures to an East Asian culture.ĢD:4D Ratios as a Marker for Prenatal Androgen Exposure More recently, aggressive/antisocial behavior and its neurobiological foundations have been examined and fetal androgen exposure, indirectly measured by the second to fourth finger length digit ratio (2D:4D), has been implicated in developmental psychopathology. These factors include fetal exposure to malnutrition ( Neugebauer, Hoek, & Susser, 1999), nicotine ( Brennan, Grekin, Mortensen, & Mednick, 2002), and lead ( Dietrich, Ris, Succop, Berger, & Bornschein, 2001). Within this context, increasing evidence has accumulated for an association between prenatal risk factors and later psychopathology. In recent years it has become increasingly apparent that multiple levels of analysis can provide important insights into both the development of behavior problems in children and resilience under stress ( Cicchetti, 2010). The results provide limited cross-cultural support for the importance of prenatal androgen exposure in contributing to the development of externalizing behavior problems in children, and they suggest that such effects may be specific to boys who may be relatively more vulnerable to early prenatal influences. These findings are the first to establish a relationship between an indirect indicator of fetal androgen exposure and any child psychopathology in Chinese children, and the observed effect size in boys was stronger than in male adults in Western studies. The effects remained significant after controlling for early adversity. Increased aggression and attention problems were both significantly associated with a lower ratio of the length of the second finger digit relative to the fourth digit ratios in boys but not girls. The ratio of the length of the second finger digit relative to the fourth digit, which is a marker for prenatal testosterone exposure, was assessed in 239 male and female fifth grade schoolchildren from Jintan, China, together with parent and teacher ratings of aggression and attention problems. This study tests the hypothesis that increased prenatal androgen exposure is associated with aggressive behavior and attention problems in childhood. It is less clear whether this association holds for childhood externalizing behavior. Prenatal androgen exposure has been associated with aggressive behavior in adults.
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