ABSTRACT
The disorder of autism is associated with a strong genetic component (Bailey, Palferman, Heavey, & Le Couteur, 1998; Szatmari, Jones, Zwaigenbaum, & MacLean, 1998) and with a unique environmental-familial experience (Rutter et al., 1997) requiring adjustment on all levels. On the average, children in the same family share 50% of their genes. Environmentally, the shared component is defined as that part of the environment that makes siblings similar to each other (e.g., social-economic status, parental characteristics), whereas the nonshared component refers to the independent aspects of the sibling environment (e.g., living with a sibling with a disability) (Anderson, Hetherington, Reiss, & Howe, 1994). Thus, due to the combined effects of these factors, siblings of children with autism have a higher risk for the development of impairments on a genetic and environmental basis.
