The 2 to 4 digit ratio (2D:4D) and eating disorder diagnosis in women

Maternal sex-hormone exposure and the risk of eating disorders in daughters

Potential effects of prenatal sex hormones on later eating disorders in offspring have been investigated with two indirect methods (finger length ratio, opposite- versus same-sex twins). We utilized a direct, prospective method, examining the association between prenatal sex-hormones in maternal sera and the risk of bulimia nervosa (BN) and anorexia nervosa (AN) among daughters. Females with BN (55), AN (150), sister controls without eating disorders (one per case), and population controls (one per case) were derived from Finnish registers. Maternal gestational testosterone and estradiol levels were assayed from archived specimens stored in a national serum biobank. When females with BN were compared to their sister controls, those with higher gestational testosterone levels were at an increased risk of BN. No significant associations with BN were found when the comparison was made to population controls, and when estradiol levels and testosterone/estrogen ratio were assessed. We neither found associations between gestational sex-hormone levels and the risk of AN. Among females with familial liability for BN, higher gestational testosterone exposure may have a role in later development of BN, whereas lower testosterone exposure may have a protective effect. We found no evidence for the involvement of gestational sex-hormones in the etiology of AN.

Sex-specific association between prenatal androgenization (second-to-fourth digit length ratio) and frontal brain volumes in adolescents

Prenatal androgenization associates sex-dependently with behavior and mental health in adolescence and adulthood, including risk-taking, emotionality, substance use, and depression. However, still little is known on how it affects underlying neural correlates, like frontal brain control regions. Thus, we tested whether prenatal androgen load is sex-dependently related to frontal cortex volumes in a sex-balanced adolescent sample. In a cross-sectional magnetic resonance imaging study, we examined 61 adolescents (28 males, 33 females; aged 14 or 16 years) and analyzed associations of frontal brain region volumes with the second-to-fourth digit length ratio (2D:4D), an established marker for prenatal androgenization, using voxel-based morphometry in a region-of-interest approach. Lower 2D:4D (indicative of higher prenatal androgen load) correlated significantly with smaller volumes of the right anterior cingulate cortex (r-ACC; β = 0.45) in male adolescents and with larger volumes of the left inferior frontal gyrus orbital part (l-IFGorb; β = - 0.38) in female adolescents. The regression slopes of 2D:4D on the r-ACC also differed significantly between males and females. The study provides novel evidence that prenatal androgenization may influence the development of the frontal brain in a sex- and frontal brain region-specific manner. These effects might contribute to the well-known sex differences in risk-taking, emotionality, substance use, and depression. Future research is needed to elucidate the role of prenatal androgenization within the biopsychosocial model.

Neurodevelopmental Model Explaining Associations between Sex Hormones, Personality, and Eating Pathology

Clinical scientists have been investigating the relationships between sex hormones, personality, and eating disorders for decades. However, there is a lack of direct research that addresses whether personality mediates or moderates the relationships between sex hormones and eating pathology. Moreover, the neural mechanisms that underlie the interactive associations between these variables remain unclear. This review aims to summarize the associations between these constructs, describe a neural mechanism mediating these relationships, and offer clinical strategies for the early identification and intervention of eating disorders. The gathered evidence shows that aggressiveness, impulsivity, and obsessive-compulsiveness may mediate or moderate the relationships between sex hormones and eating pathology, but only among females. Furthermore, sex hormone receptor density in the mesocorticolimbic dopamine pathway may explain the neural mechanism of these associations. Future research should use more comprehensive personality measurements and assess the mediation and moderation effects of temperament while taking the hormone levels of women across menstrual cycles into account. Additionally, electroencephalography and functional magnetic resonance imaging should be implemented to directly assess brain activity and corroborate these findings.

The 2D:4D index is associated with the development of excess body weight in adults, but not with the rate of weight loss following bariatric surgery

2D:4D finger length ratio is a proxy of prenatal sex hormone exposure. Prenatal testosterone decreases and prenatal estrogens increase this index. In the current study we investigated whether the 2D:4D index, as a marker of the prenatal hormonal environment, is associated with the development of overweight and obesity in adults, and whether is it correlated with the rate of weight loss in patients after bariatric surgery. We tested 125 adults with obesity (BMI ≥ 30.0 kg/m²), 125 adults with overweight (BMI 25.0–29.9 kg/m²) and 153 persons with normal body weight (BMI < 25 kg/m²) of both sexes. We have found that the development of excessive body weight in men and women, and fat accumulation in the upper arms, thighs and lower legs in women with obesity (but not men) are associated with increased prenatal estrogen exposure. This relationship indicates a new area of activity in the field of obesity prevention. Moreover, it seems that the 2D:4D index (especially of the right hand) may be a useful factor in early prediction of the risk of developing excessive body weight in humans. The rate of weight loss after bariatric surgery is independent of prenatal exposure to sex hormones.

Gonadal Hormone Influences on Sex Differences in Binge Eating Across Development

PURPOSE OF REVIEW

Binge eating is a transdiagnostic symptom that disproportionately affects females. Sexually dimorphic gonadal hormones (e.g., estradiol, testosterone) substantially impact eating behavior and may contribute to sex differences in binge eating. We examine recent evidence for the role of gonadal hormones in binge eating risk across development.

RECENT FINDINGS

Both organizational (long-lasting impact on the central nervous system (CNS)) and activational (transient influences on the CNS) hormone effects may contribute to sex differences in binge eating. Gonadal hormones also impact within-sex variability in binge eating, with higher estradiol levels in females and higher testosterone levels in males protective across development. Emerging evidence suggests that the impact of gonadal hormones may be greatest for people with other risk factors, including genetic, temperamental (e.g., high negative affect), and psychosocial (e.g., exposure to weight-based teasing) risk. Gonadal hormones contribute to sex differences and within-sex variability in binge eating across development.

The role of prenatal and perinatal factors in eating disorders: a systematic review

Numerous studies showed that factors influencing fetal development and neonatal period could lead to lasting alterations in the brain of the offspring, in turn increasing the risk for eating disorders (EDs). This work aims to systematically and critically review the literature on the association of prenatal and perinatal factors with the onset of EDs in the offspring, updating previous findings and focusing on anorexia nervosa (AN) and bulimia nervosa (BN). A systematic literature search was performed on Pubmed, PsycINFO, and Scopus. The drafting of this systematic review was conducted following the PRISMA statement criteria and the methodological quality of each study was assessed by the MMAT 2018. A total of 37 studies were included in this review. The factors that showed a more robust association with AN were higher maternal age, preeclampsia and eclampsia, multiparity, hypoxic complications, prematurity, or being born preterm (< 32 weeks) and small for gestational age or lower birth size. BN was only associated with maternal stress during pregnancy. Many methodological flaws emerged in the considered studies, so further research is needed to clarify these inconsistencies. Altogether, data are suggestive of an association between prenatal and perinatal factors and the onset of EDs in the offspring. Nevertheless, given the methodological quality of the available literature, firm conclusions cannot be drawn and whether this vulnerability is specific to EDs or mental disorders remains to be defined. Also, a strong need for longitudinal and well-designed studies on this topic emerged.

Emotional stability is related to 2D:4D and social desirability in women: Possible implications on subjective well-being and psychopathology

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.

Second-to-Fourth Digit Ratio (2D:4D) in Psychiatric Disorders: A Systematic Review of Case-control Studies

The second-to-fourth digit ratio (2D:4D) is an indirect, retrospective, non-invasive measure that correlates negatively with intrauterine exposure to testosterone. The present meta-analysis aimed to evaluate if 2D:4D differs between patients with psychiatric disorders and controls. In September 2019, we searched in Web of Knowledge, PsycINFO, Embase, and CINHAL, and retrieved 619 papers. We finally included 43 case-control studies which compared the 2D:4D ratio of patients with autism spectrum disorder (ASD) (n = 16), schizophrenia (n = 8), gender non-conformity (n = 7), addictions (n = 5), attention deficit-hyperactivity disorder (ADHD) (n = 4), mood disorders (n = 2), and intellectual disability (n = 1) to non-clinical controls. Meta-analyses showed that, overall, psychiatric patients had lower 2D:4D than healthy controls (n = 43, overall sample = 9,484, mean difference = -0.0056, 95% confidence interval from -0.0093 to -0.002, I2 = 74%), with more pronounced differences in the right hand, males, and children. Considering psychiatric disorders individually, significant differences were found in the ASD, ADHD, and addictions groups, in which 2D:4D was significantly lower than healthy controls. Conversely, the right hand of males with schizophrenia showed higher 2D:4D than healthy controls. No other significant differences were detected. Although our results need to be cautiously interpreted and find limited applications in clinical practice, they may suggest that 2D:4D is altered in some psychopathological conditions, underlining the role of prenatal exposure to sex steroids in the etiology of psychiatric disorders.

Gonadal hormone contributions to individual differences in eating disorder risk

PURPOSE OF REVIEW

Females experience eating disorders at substantially higher rates than males. Although sociocultural factors have traditionally been thought to underlie this sex disparity, accumulating evidence implicates differential exposure to gonadal hormones early in life. Gonadal hormones also impact within-sex variability in disordered eating, helping to explain why not all women develop an eating disorder, and some men do. We review recent findings regarding these gonadal hormone effects and their implications for the etiology of eating disorders.

RECENT FINDINGS

Males are exposed to significantly higher testosterone levels than females perinatally, and this exposure appears to protect against later binge eating in males relative to females. Within-sex, higher estradiol levels among females and higher testosterone levels among males appear to be protective. Progesterone exhibits minimal direct phenotypic effects on disordered eating but appears to counteract the protective effects of estrogen in adult females. Importantly, gonadal hormone effects may be moderated by psychosocial factors.

SUMMARY

Evidence suggests that gonadal hormones play a critical role in the etiology of disordered eating. Overall, higher testosterone and estrogen appear to be protective across development. Additional research is needed to identify mechanisms underlying these effects and further explore interactions between hormonal and psychosocial risk.

Eating Disorders: An Evolutionary Psychoneuroimmunological Approach

Eating disorders are evolutionarily novel conditions. They lead to some of the highest mortality rates of all psychiatric disorders. Several evolutionary hypotheses have been proposed for eating disorders, but only the intrasexual competition hypothesis is extensively supported by evidence. We present the mismatch hypothesis as a necessary extension to the current theoretical framework of eating disorders. This hypothesis explains the evolutionarily novel adaptive metaproblem that has arisen when mating motives conflict with the large-scale and easy availability of hyper-rewarding but obesogenic foods. This situation is exacerbated particularly in those contemporary environments that are characterized by sedentary lifestyles, ever-present junk foods, caloric surplus and the ubiquity of social comparisons that take place via social media. Our psychoneuroimmunological model connects ultimate-level causation with proximate mechanisms by showing how the adaptive metaproblem between mating motives and food rewards leads to chronic stress and, further, to disordered eating. Chronic stress causes neuroinflammation, which increases susceptibility to OCD-like behaviors that typically co-occur with eating disorders. Chronic stress upregulates the serotonergic system and causes dysphoric mood in anorexia nervosa patients. Dieting, however, reduces serotonin levels and dysphoric mood, leading to a vicious serotonergic-homeostatic stress/starvation cycle whereby cortisol and neuroinflammation increase through stringent dieting. Our psychoneuroimmunological model indicates that between-individual and within-individual variation in eating disorders partially arises from (co)variation in gut microbiota and stress responsivity, which influence neuroinflammation and the serotonergic system. We review the advances that have been made in recent years in understanding how to best treat eating disorders, outlining directions for future clinical research. Current evidence indicates that eating disorder treatments should aim to reduce the chronic stress, neuroinflammation, stress responsivity and gut dysbiosis that fuel the disorders. Connecting ultimate causes with proximate mechanisms and treating biopsychosocial causes rather than manifest symptoms is expected to bring more effective and sophisticated long-term interventions for the millions of people who suffer from eating disorders.

Social Media, Thin-Ideal, Body Dissatisfaction and Disordered Eating Attitudes: An Exploratory Analysis

Disordered eating attitudes are rapidly increasing, especially among young women in their twenties. These disordered behaviours result from the interaction of several factors, including beauty ideals. A significant factor is social media, by which the unrealistic beauty ideals are popularized and may lead to these behaviours. The objectives of this study were, first, to determine the relationship between disordered eating behaviours among female university students and sociocultural factors, such as the use of social network sites, beauty ideals, body satisfaction, body image and the body image desired to achieve and, second, to determine whether there is a sensitive relationship between disordered eating attitudes, addiction to social networks, and testosterone levels as a biological factor. The data (N = 168) was obtained using validated surveys (EAT-26, BSQ, CIPE-a, SNSA) and indirect measures of prenatal testosterone. The data was analysed using chi-square, Student’s t-test, correlation tests and logistic regression tests. The results showed that disordered eating attitudes were linked to self-esteem (p < 0.001), body image (p < 0.001), body desired to achieve (p < 0.001), the use of social media (p < 0.001) and prenatal testosterone (p < 0.01). The findings presented in this study suggest a relationship between body image, body concerns, body dissatisfaction, and disordered eating attitudes among college women.

Cross-national gender variations of digit ratio (2D:4D) correlate with life expectancy, suicide rate, and other causes of death

The second-to-fourth finger length ratio (2D:4D) is an indication of prenatal sex hormone exposure, and has sex-specifically been associated with several lethal illnesses including ischemic heart disease, diverse cancers, and suicide. Our primary aim was to verify that 2D:4D sex-specifically relates to life expectancy and suicide numbers on a national level (23 countries). We also used a hypothesis-free approach to investigate associations with other causes of death [p value adjustment for multiple hypothesis testing using the false discovery rate procedure (FDR)]. All parameters were normalized to the national mean (of males and females) and analyzed across nations. Normalized male 2D:4D correlated positively with normalized male life expectancy (at birth, r = 0.46, p = 0.029; at the age of 60, r = 0.44, p = 0.038) and negatively with normalized male suicide rates (r = − 0.49, p = 0.017). In the exploratory analyses, the normalized male 2D:4D values were negatively associated with the normalized male deaths rates from communicable, maternal, perinatal, and nutritional conditions [r = − 0.65, p(FDR) = 0.011], respiratory infections [r = − 0.69, p(FDR) = 0.008], asthma [r = − 0.65, p(FDR) = 0.011], neurological conditions [r = − 0.56, p(FDR) = 0.046], and Alzheimer’s disease and other dementias [r = − 0.59, p(FDR) = 0.036]. The normalized female parameters showed the same cross-national correlations. In line with the previous individual level findings, the results suggest that prenatal sex hormone effects are sex-specifically involved in suicide and neurological conditions. Moreover, we provide novel national level evidence that prenatal sex hormone priming may sex-specifically influence life expectancy and death risk from respiratory diseases.

Sex Differences in Binge Eating: Gonadal Hormone Effects Across Development

Eating disorders are highly sexually differentiated disorders that exhibit a female predominance in risk. Most theories focus on psychosocial explanations to the exclusion of biological/genetic influences. The purpose of this descriptive review is to evaluate evidence from animal and human studies in support of gonadal hormone effects on sex differences in binge eating. Although research is in its nascent stages, findings suggest that increased prenatal testosterone exposure in males appears to protect against binge eating. Although pubertal testosterone may exert additional protective effects, the prenatal period is likely critical for the decreased risk observed in males. By contrast, studies indicate that, in females, it is the lack of prenatal testosterone coupled with the organizational effects of pubertal ovarian hormones that may lead to increased binge eating. Finally, twin data suggest that changes in genetic risk may underlie these hormone influences on sex differences across development.

The relationship between second-to-fourth digit (2D:4D) ratios and problematic and pathological Internet use among Turkish university students

Background and aims The ratio of the second and fourth fingers (2D:4D ratio) is a sexually dimorphic trait, with men tending to have lower values than women. This ratio has been related to prenatal testosterone concentrations and addictive behaviors including problematic video-gaming. We aimed to investigate the possible association between 2D:4D ratios and Internet addiction and whether such a relationship would be independent of impulsivity. Methods A total of 652 university students (369 women, 283 men), aged 17-27 years, were enrolled in the study. Problematic and pathological Internet use (PPIU) was assessed using the Internet Addiction Test (IAT). The participants also completed the Barratt Impulsiveness Scale (version 11; BIS-11) and had their 2D:4D ratios measured. Results 2D:4D ratios were not significantly different in women with PPIU and in those with adaptive Internet use (AIU). Men with PPIU exhibited lower 2D:4D ratios on both hands when compared with those with AIU. Correlation analysis revealed that 2D:4D ratios on both hands were negatively correlated with IAT scores among men, but not among women. The multiple linear regression analysis revealed that age, duration of weekly Internet use, impulsiveness, and 2D:4D ratios on the right hand were independently associated with IAT scores among men, and impulsivity did not mediate the relationship between 2D:4D ratios and PPIU. Conclusions For men, 2D:4D ratios on the right hand were inversely correlated with Internet addiction severity even after controlling for individual differences in impulsivity. These findings suggest that high prenatal testosterone levels may contribute to the occurrence of PPIU among men.

Age differences in prenatal testosterone's protective effects on disordered eating symptoms: developmental windows of expression?

Prenatal testosterone exposure may be protective against disordered eating. However, prior studies have produced mixed results. Developmental differences in prenatal testosterone's protective effects on disordered eating may explain these discrepancies. Indeed, studies have differed in the age of participants assessed, with data supporting prenatal testosterone effects on disordered eating in early adolescent and young adult samples but not in late adolescence. The present studies are the first to investigate age differences in prenatal testosterone's protective effects on disordered eating. Two indirect markers of higher prenatal testosterone were examined: (a) lower finger-length ratios (Study 1: index [2D]/ring [4D] finger [2D:4D]) and (b) lower disordered eating in female s from opposite-sex twin pairs (who are thought to be exposed to higher prenatal testosterone from their male co-twin) relative to female controls (Study 2). Participants were twins from the Michigan State University Twin Registry (Study 1: n = 409; Study 2: n = 1,538) in early adolescence, late adolescence, or young adulthood. Disordered eating was assessed with well-validated questionnaires. Finger-length ratios were measured from hand scans, using electronic computer calipers. Findings were consistent across both studies. Higher prenatal testosterone (lower 2D:4D; females from opposite-sex twin pairs vs. controls) predicted lower disordered eating in early adolescence and young adulthood only. Prenatal testosterone-disordered eating associations were not observed during late adolescence. Results point to the possibility of developmental windows of expression for prenatal testosterone's protective effects on disordered eating and suggest that prior discrepant results may reflect age differences across samples.

Prenatal and perinatal factors in eating disorders: a descriptive review

OBJECTIVE

The objective of this descriptive review is to summarize the current scientific evidence on various prenatal and perinatal exposures affecting later development of eating disorders among offspring.

METHOD

Studies were searched from PubMed database with the following keywords: eating disorders and disordered eating and anorexia nervosa and bulimia nervosa and binge eating disorder and prenatal exposure delayed effects and maternal exposure and perinatology. A comprehensive manual search, including search from the reference list of included articles, was also performed.

RESULTS

The attributable risk for prenatal and perinatal factors in anorexia nervosa (AN) is 3.6%. Numerous prenatal and perinatal factors have been associated with offspring AN, but only prematurity has been replicated in different samples. The risk of bulimia nervosa (BN) in offspring has attracted less study, and despite varying positive associations, there are no replicated findings. Higher prenatal testosterone may protect against the development of a range of disordered eating symptoms, although studies are not consistent.

DISCUSSION

Evidence in support of an effect of prenatal and perinatal factors on eating disorders or disordered eating in offspring is conflicting. If present, the overall effect appears to be relatively small, and it is likely that the early risk factors operate in conjunction with other biological, genetic, and/or environmental risk factors to bring on eating pathology. Genetically sensitive designs, such as sibling and twin studies, are needed to disentangle the different types of risk factors and ensure that prenatal/perinatal effects are "causal" rather than indications of genetic risk.

Prenatal testosterone of progenitors could be involved in the etiology of both anorexia nervosa and autism spectrum disorders of their offspring

OBJECTIVES

High intrauterine testosterone (T) levels seem to play a role in the development of autism spectrum disorders (ASDs), but their role in anorexia nervosa (AN) is controversial. Parents with masculinized 2D:4D ratios, a marker of the organizational effects of T, may have other relevant biological characteristics, in particular exposing their offspring to high T levels in the prenatal environment. This would increase the likelihood of their offspring developing these disorders.

METHODS

The present study examined whether parents of offspring with AN (n=34; mean age= 51) and ASD (n=36; mean age=45) differ from control parents (n=40; mean age=43) in 2D:4D ratio, as well as by salivary T levels and its relationships.

RESULTS

Our results revealed that AN and ASD parents (fathers and mothers) have masculinized 2D:4D ratios of the right hand compared to control parents. However, the difference compared to controls was larger in the ASD than the AN group. Furthermore, current salivary T levels were negatively related to the 2D:4D ratio in ASD and AN parents only.

CONCLUSIONS

Our data partially support the view of high prenatal masculinization as a potential intermediate phenotype to the development of these disorders in their offspring.

The role of reproductive hormones in the development and maintenance of eating disorders

Much remains to be understood about the etiology of eating disorders. There is substantial evidence that reproductive hormones, specifically estrogens, play a direct role in normal food intake. Evidence is increasing that the reproductive hormones play a role in the abnormal food intake associated with eating disorders. For example, there is an inverse association between estradiol and eating disorder symptoms. Preliminary studies also suggest that hormone augmentation may be a beneficial adjunct to the standard treatment of choice for eating disorders. However, research is limited, so definitive conclusions about the benefit of hormone augmentation in treatment cannot be drawn. Future research, with a focus on translational studies, should continue to explore the role of reproductive hormones in the vulnerability to and maintenance of eating disorders.

2D:4D ratio in children at familial high-risk for eating disorders: The role of prenatal testosterone exposure

OBJECTIVES

Markers of prenatal hormone exposure have been associated with the development of eating disorder (ED) behaviors. Our aim was to determine whether 2D:4D ratio, a marker for in utero testosterone exposure, is associated with risk for ED in a large population-based cohort: the Avon Longitudinal Study of Parents and Children (ALSPAC).

METHODS

This is the first study to investigate prenatal testosterone exposure in children at high-risk for ED, using 2D:4D as a marker. We compared children whose mothers reported a lifetime ED (anorexia, bulimia, or both; N = 446) to children whose mothers did not (n = 5,367).

RESULTS

Daughters of women with lifetime bulimia nervosa (BN) had lower 2D:4D ratio (B: -0.01, 95% CI: -0.02 to -0.002, P = 0.02), indicating higher prenatal testosterone exposure, than daughters of mothers unaffected by ED. No differences were observed in the male children of women with an ED.

CONCLUSIONS

Findings suggest that children at high-risk for BN may be exposed to higher levels of testosterone in utero. Fetal exposure to androgen excess is thought to be causal in the development of polycystic ovary syndrome (PCOS), a disorder which is highly comorbid with binge eating and BN. Future research should investigate the potential role of testosterone exposure in utero as a risk factor for BN and binge eating.

Sex differences in the physiology of eating

Hypothalamic-pituitary-gonadal (HPG) axis function fundamentally affects the physiology of eating. We review sex differences in the physiological and pathophysiological controls of amounts eaten in rats, mice, monkeys, and humans. These controls result from interactions among genetic effects, organizational effects of reproductive hormones (i.e., permanent early developmental effects), and activational effects of these hormones (i.e., effects dependent on hormone levels). Male-female sex differences in the physiology of eating involve both organizational and activational effects of androgens and estrogens. An activational effect of estrogens decreases eating 1) during the periovulatory period of the ovarian cycle in rats, mice, monkeys, and women and 2) tonically between puberty and reproductive senescence or ovariectomy in rats and monkeys, sometimes in mice, and possibly in women. Estrogens acting on estrogen receptor-α (ERα) in the caudal medial nucleus of the solitary tract appear to mediate these effects in rats. Androgens, prolactin, and other reproductive hormones also affect eating in rats. Sex differences in eating are mediated by alterations in orosensory capacity and hedonics, gastric mechanoreception, ghrelin, CCK, glucagon-like peptide-1 (GLP-1), glucagon, insulin, amylin, apolipoprotein A-IV, fatty-acid oxidation, and leptin. The control of eating by central neurochemical signaling via serotonin, MSH, neuropeptide Y, Agouti-related peptide (AgRP), melanin-concentrating hormone, and dopamine is modulated by HPG function. Finally, sex differences in the physiology of eating may contribute to human obesity, anorexia nervosa, and binge eating. The variety and physiological importance of what has been learned so far warrant intensifying basic, translational, and clinical research on sex differences in eating.

Postnatal testosterone levels and disorder relevant behavior in the second year of life

The objective of the current study was to investigate the relationship between testosterone collected at 3-4 months of age and sex-linked disorder-relevant behaviors in the second year of life. Eighty-four children participated at 3-4 (when salivary testosterone levels were obtained and second to fourth digit ratios were measured) and 18-24 months of age (when behavioral ratings of aggression and verbal ability were coded from two 8-min play sessions). Parents also completed the Brief Infant-Toddler Social and Emotional Assessment, and the four subscales (Internalizing, Externalizing, Dysregulation, and Autism Spectrum Disorder) were used to indicate child specific problems. Greater postnatal testosterone levels in early infancy were predictive of more male-typical behaviors in the second year of life (i.e., more autism spectrum behaviors, less time vocalizing, and more Internalizing Problems). These results support the hypothesis that early infancy may be another critical period for the development of gender-linked behavior.

From one extreme to the other: negative evaluation anxiety and disordered eating as candidates for the extreme female brain

Simon Baron-Cohen pioneered the idea that different brain types evolved to process information in gender specific ways. Here we expand this approach to looking at eating disorders as a byproduct of the extreme female brain. The incidence of eating disorders is higher among females, and recent findings show that hormones may play a role in eating disorders. We present new evidence from four studies that both an empathizing bias and hyper-mentalizing (as measures of the extreme female brain; EFB) are related to disordered eating and negative evaluation anxiety in women. We also advance the novel hypothesis that concerns about animal welfare (a unique expression of the EFB) may account for the relationship between vegetarianism and eating disorders.

From One Extreme to the Other: Negative Evaluation Anxiety and Disordered Eating as Candidates for the Extreme Female Brain

Simon Baron-Cohen pioneered the idea that different brain types evolved to process information in gender specific ways. Here we expand this approach to looking at eating disorders as a byproduct of the extreme female brain. The incidence of eating disorders is higher among females, and recent findings show that hormones may play a role in eating disorders. We present new evidence from four studies that both an empathizing bias and hyper-mentalizing (as measures of the extreme female brain; EFB) are related to disordered eating and negative evaluation anxiety in women. We also advance the novel hypothesis that concerns about animal welfare (a unique expression of the EFB) may account for the relationship between vegetarianism and eating disorders.