Plain-language explanation.
Neurodevelopment describes how the brain develops from conception through adulthood. The brain undergoes dramatic changes in early life — billions of neurons form, connect, and are pruned away. Early experiences profoundly shape brain development. Disruptions to normal development can cause conditions like autism spectrum disorder or ADHD.
Core concepts and standard treatment.
Neurodevelopmental milestones: neural tube closure, neurogenesis (prenatal peak), cortical migration, synaptogenesis (peak postnatal, extending through adolescence), myelination (birth through early adulthood), and synaptic pruning (adolescent refinement of neural circuits). Critical and sensitive periods for specific capacities (vision, language, social bonding) represent windows of heightened plasticity and vulnerability.
Deeper theory, debates and edge cases.
Genetic and environmental influences on neurodevelopment: GWAS have identified hundreds of common variants each contributing small risk for ASD, ADHD, schizophrenia. Rare copy number variants (CNVs) confer large individual risks. Epigenetic mechanisms (DNA methylation, histone modification) translate environmental exposures (prenatal stress, nutrition, toxins, infection) into stable changes in gene expression and neural circuit development. The "two-hit" hypothesis proposes that neurodevelopmental disorders require both genetic vulnerability and environmental insult.
How it is applied in practice.
Autism spectrum disorder (ASD) is a highly heterogeneous spectrum with shared behavioural phenotype but diverse genetic, neural, and cognitive mechanisms. Early intervention (ABA, ESDM, pivotal response training) in the critical developmental window significantly improves outcomes. ADHD involves prefrontal-striatal-cerebellar circuit immaturity and dopaminergic-noradrenergic dysregulation. Adverse childhood experiences (ACEs) — abuse, neglect, household dysfunction — alter stress response system development with lasting physical and mental health consequences, mediated through epigenetic and neural circuit mechanisms.