| Prevalence |
Up to 1% of the population has ASD, but among children and adolescents (which is a younger cohort), the estimate is closer to 2% (Blumberg et al., 2013). The reported prevalence of ASD is increasing (Atladóttir, 2007; Hertz-Picciotto & Delwiche, 2009), at least in part because of earlier diagnosis of the disorder (Parner et al., 2008). |
| Onset |
Symptoms usually arise during infancy (Ozonoff et al., 2008). However, symptoms may not be recognized until the second year of life (or earlier, if symptoms are severe). |
| Comorbidity |
Between 50% and 70% of people with ASD also have intellectual disability (Sigman et al., 2006). However, some researchers believe the high comorbidity is an overestimate (Edelson, 2006), particularly because people with ASD tend to have higher IQs when tested using nonverbal IQ tests. |
| Course |
Children with ASD often improve in some areas of functioning during the elementary school years (Shattuck et al., 2007). During adolescence, some children’s symptoms worsen, whereas other children’s symptoms improve (Fountain et al., 2012). |
| Gender Differences |
Males are four times more likely than females to develop ASD. |
| Source: Unless otherwise noted, the source for information is American Psychiatric Association, 2013. |