Fragile X syndrome (FXS), the leading heritable cause of intellectual disability, has a co-occurrence rate of autism spectrum disorder (ASD) estimated at ~60%. The onset and rates of motor development in FXS are slower relative to neurotypical development, and even more so in the context of co-occurring FXS + ASD. Extant evidence suggests these…

Individuals with autism spectrum disorder are more likely than typically developing individuals to experience a range of gastrointestinal abnormalities, including chronic diarrhea, constipation, food sensitivities, and abdominal pain. These gastrointestinal symptoms have been associated with higher levels of irritability and aggressive behavior,…

Epilepsy is common in children with autism spectrum disorder (ASD) but little is known about how seizures impact the autism phenotype. The association between epilepsy and autism symptoms and associated maladaptive behaviors was examined in 2,645 children with ASD, of whom 139 had epilepsy, from the Simons Simplex Collection. Children with ASD and…

Autism spectrum disorder and attention deficit hyperactivity disorder are neurodevelopmental disorders that cannot be codiagnosed under existing diagnostic guidelines ("Diagnostic and Statistical Manual of the American Psychiatric Association," 4th ed., text rev.). However, reports are emerging that attention deficit hyperactivity…