Traits and genetic factors associated with autism spectrum disorders are common in the general population and siblings of patients and are not limited to individuals with the actual diagnosis. Nor is the genetic influence limited to the autism spectrum. St. Pourcain et al. (CME, p. 1364) found that a genetic variant previously linked to the diagnosis influences the trait of social communication in the general population. Among 7,313 children ages 3-12 years, the variant was also associated with a profile including subthreshold impairments in social, communicative, and cognitive abilities. In 1,235 families with an autistic child, Constantino et al. (p. 1349) discovered that 20% of siblings classified as unaffected had language delays plus autistic speech. Such siblings were more common in families having multiple children diagnosed with autism spectrum disorders. The twin study by Lichtenstein et al. (p. 1357) showed that concordance rates for autism spectrum disorders, ADHD, developmental coordination disorder, and tic disorder were greater in monozygotic than dizygotic pairs. Cross-disorder effects were also greater in monozygotic pairs, and a substantial proportion of the genetic variance for autism spectrum disorders was shared with the other disorders (figure). The editorial by Kendler (p. 1291) points out that these findings have emerged because studies of the heritability of autism have encompassed larger numbers of families.

Public awareness of the neurobiology of mental illness increased between 1996 and 2006, yet the stigma associated with several major mental disorders did not decline. Pescosolido et al. (p. 1321) found that persons who have a neurobiological conception of schizophrenia or depression actually had increased likelihood of aversion or fear in their rating of vignettes of individuals with these illnesses. The perception of alcohol dependence as refl ecting "bad character" rose from 49% to 65% of survey respondents. Support for treatment increased, however, and in an editorial, Goldman (p. 1289) suggests that the outcome of the study would have been different if the vignettes had included individuals who have recovered from mental illness.