The Sex Ratio of Full and Half Siblings of People Diagnosed With ADHD in Childhood and Adolescence: A Danish Nationwide Register-Based Cohort Study

Sex and gender in neurodevelopmental conditions

Health-related conditions often differ qualitatively or quantitatively between individuals of different birth-assigned sexes and gender identities, and/or with different gendered experiences, requiring tailored care. Studying the moderating and mediating effects of sex-related and gender-related factors on impairment, disability, wellbeing and health is of paramount importance especially for neurodivergent individuals, who are diagnosed with neurodevelopmental conditions with uneven sex/gender distributions. Researchers have become aware of the myriad influences that sex-related and gender-related variables have on the manifestations of neurodevelopmental conditions, and contemporary work has begun to investigate the mechanisms through which these effects are mediated. Here we describe topical concepts of sex and gender science, summarize current knowledge, and discuss research and clinical challenges related to autism, attention-deficit/hyperactivity disorder and other neurodevelopmental conditions. We consider sex and gender in the context of epidemiology, behavioural phenotypes, neurobiology, genetics, endocrinology and neighbouring disciplines. The available evidence supports the view that sex and gender are important contributors to the biological and behavioural variability in neurodevelopmental conditions. Methodological caveats such as frequent conflation of sex and gender constructs, inappropriate measurement of these constructs and under-representation of specific demographic groups (for example, female and gender minority individuals and people with intellectual disabilities) limit the translational potential of research so far. Future research and clinical implementation should integrate sex and gender into next-generation diagnostics, mechanistic investigations and support practices.

22q12.3 microduplication overlapping the LARGE gene as a male-only affected loci responsible for increasing the risk of autism spectrum disorder

The present study describes a three-generation Chinese family with one male who was diagnosed with an autism spectrum disorder (ASD) disease. The male proband presented with features of an autism spectrum disorder. Magnetic resonance imaging demonstrated an abnormal high-intensity zone in the frontal white matter. Whole-genome single nucleotide polymorphism-microarray demonstrated an interstitial 575-kb duplication of chromosome 22p12.3 that involved the LARGE gene among the six family members, which included three healthy female carriers, the affected boy and two male fetuses. Fluorescence in situ hybridization analysis, using special probes, and LARGE gene sequencing were performed, which exhibited a submicroscopic 22q13 duplication that involved the LARGE gene. Combined with a review of the literature, the present findings support the hypothesis that the 22q12.3 microduplication overlapping the LARGE gene may be a male-only affected loci, which is responsible for increasing the ASD risk.

A review of the established and suspected causes of variations in human sex ratio at birth

The human sex ratio (proportion male) at birth (SRB) varies with many variables. Some of this variation has an established proximate cause. For instance, low SRB (more females) at birth are associated with various forms of stressful events or circumstances during or prior to pregnancy. These low SRB are almost certainly mainly caused by maternal-stress-induced male foetal loss. Other types of SRB variation are thought to be caused by hormonal variation in either or both parents around the time of conception. One or other of these two types of proximate cause seems to be responsible for most of the established variation of SRB. This will be illustrated here in respect of some selected forms of SRB variation. It seems likely that a clarification of the hormonal causes of SRB variation will also help explain the striking (apparent) inconsistencies in the results of reported tests of the influential Trivers-Willard hypothesis. It is further proposed that an appreciation of the evidence that parental hormones influence SRB may enhance understanding of several important pathologies (hepatitis B, toxoplasmosis, testicular cancer, prostate cancer and autism).