Current figures show that autism occurs in all racial, ethnic, and social groups equally, with individuals in one group no more or less likely to have ASDs than those in other groups. 

Three groups are at higher-than-normal risk for ASDs, including:

• Boys.  Statistics show that boys are three to four times more likely⁵ to be affected by autism than girls are. 
• Siblings of those with ASDs.  Among families that have one child with an ASD, recurrence of ASD in another sibling is between⁶ 2 percent and 8 percent, a figure much higher than in the general population.
• People with certain other developmental disorders.  For certain disorders, including Fragile X syndrome, mental retardation, and tuberous sclerosis, autism is common in addition to the primary symptoms of the disorder.