ASD is a spectrum because its expression differs profoundly across individuals. Contributing factors include:
- Neurological Diversity: Core domains (social communication, restricted/repetitive behaviors, sensory processing) vary in severity and combination.
- Co-occurring Conditions: ADHD, ID, anxiety, epilepsy, GI issues modify presentation.
- Genetic Heterogeneity: Hundreds of risk genes (common variants + rare mutations) create diverse neurodevelopmental trajectories.
- Epigenetics: Environmental influences on gene expression (prenatal infection, stress, toxins) add variability.
- Environmental Factors: Pre/perinatal complications, maternal immune activation, prematurity.
- Developmental Timing: When and how neural circuits diverge shapes phenotype.
This complexity demands individualized assessment, intervention, and support—no single approach fits all.
