Mental retardation

A neurodevelopmental disorder characterized by significantly subaverage intellectual functioning (IQ <70), with concurrent impairments in adaptive behavior (conceptual, social, and practical skills), and onset during the developmental period (before 18 years of age). Possible causes are genetic (Down syndrome, Fragile X syndrome, phenylketonuria), factors during pregnancy (Fetal Alcohol Spectrum disorder, rubella, CMV, syphilis, malnutrition, illicit drugs, environmental heavy metals), factors during childbirth (hypoxia, extreme prematurity), factors after birth (meningitis/encephalitis, traumatic brain injury, lead/mercury poisoning).