The purpose of this research study is to learn more about the outcomes of children who received an Autism Spectrum Disorder (ASD) diagnosis when they were toddlers. The study is interested in whether an early diagnosis can help children with their cognitive, language, social, and behavioral abilities.

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by deficits in domains of social communication and restrictive and repetitive behavior. There is general agreement, in light of knowledge around optimal periods of neural plasticity, that ASD should be diagnosed as early as possible since young toddlers are at a critical stage in early development when intervention is theoretically most effective. The rate of persistence of an ASD diagnosis is heavily debated.Therefore this study attempts:

1. To determine the rate of persistence of Autism Spectrum Disorder (ASD) diagnosis and functional outcomes, as defined by cognitive level, adaptive functioning, language skills, persistence of ASD symptoms, and classroom placement at kindergarten age, among children who received a DSM-5 ASD diagnosis at < 36 months.
2. To evaluate predictors of rate of persistence and functional outcomes among kindergarten grade level children ages 5-7 years, who received an ASD diagnosis as toddlers.

Inclusion Criteria:

• Diagnosed with Autism Spectrum Disorder as a toddler through DSM-5 at Boston Children's Hospital
• Enrolled in or just finished Kindergarten

Exclusion Criteria:

• Individuals with known genetic disorders including, but not limited to, Fragile X syndrome, Down syndrome, Tuberous Sclerosis Complex and those with 16 p deletions/duplications.

Children diagnosed with Autism Spectrum Disorder through the DSMV as toddlers.