Developmental disabilities are conditions that originate before age 18 and affect major life activities. They include intellectual disabilities and conditions such as Down syndrome, fragile X syndrome, autism, fetal alcohol spectrum disorder, and cerebral palsy. People with developmental disabilities often face physical and mental health issues, abuse and vulnerability, and challenging behaviors. They are also at higher risk for mental health problems. Effective support requires treating individuals with dignity while addressing both their disability and any mental health needs.