ASD have a prevalence of 1.5% (Baird et al. 2006), and are characterized by deficits in (i) reciprocal social interaction and (ii) communication and by (iii) restricted, repetitive and stereotyped patterns of behavior, interests and activities (DSM-IV-TR, APA, 2000). Symptoms in the latter domain include a strong interest in non-functional routines or rituals, preoccupations with one narrow topic, and stereotyped and repetitive motor behaviors and body movements. ASD have onset prior to age 3 years, and a strong persistence over time in older childhood, over adolescence and into adulthood. Twin studies indicate that the phenotypic and genetic overlap between the three symptom domains of ASD, social behavior, communication, and repetitive and stereotyped behaviors, is very modest (Ronald et al., 2006a,b). Between 25 and 50% of subjects with ASD have clinically impairing symptoms of impulsivity, inattention and hyperactivity that pass diagnostic thresholds for attention-deficit hyperactivity disorder (ADHD) (Rommelse et al., 2010). Subjects with ASD have a 3-fold increased risk to develop addictive behaviors in adolescence.