• Approximately 70% of individuals with ASD have at least one comorbid mental illness and 40% have two or more (Simonoff et al., 2008).

• Adults with comorbid ASD and ID are at greater risk for behavior problems than individuals with ID:

• Griffith et al. (2010) found that children with ASD had significantly more behavior problems than either children with DS or children with ID.

• Esbensen et al. (2008) found that adults with DS had fewer behavior problems and less externalizing problem behaviors compared with adults with ID alone.

• Tassé et al. (2016) reported a similar trend in their sample of adults with DS, reporting a lower prevalence rate of co-occurrence of mental and behavioral health issues than a comparable group of adults with idiopathic ID.

Note: This study was in the article that I read.