Autism spectrum disorder (ASD) is a complex developmental disorder which appears early during childhood and is characterized by core symptoms, which consist of persistent social deficits and restricted, repetitive types of behavior, interests, or activities. These latter symptoms are frequently associated with other emotional symptoms such as anxiety, irritability, mood lability, and sleep difficulties, which may lead to functional impairment and significant burden for caregivers. ASD affects about 1% of the general population (1 out of 68 children) and is three to four times more prevalent in males than in females.1,2

ASD may be associated with multiple comorbidities, including intellectual disability, anxiety, attention deficit/hyperactivity disorder, and epilepsy, as well as medical comorbidities including major congenital anomalies. Syndromic ASD is usually defined as a disorder with a clinically defined pattern of somatic abnormalities and a neurobehavioral phenotype that may include ASD. In this latter case, the diagnosis is confirmed by targeted genetic testing.

There is clear evidence for a genetic component of ASD. Children having siblings with ASD have worse linguistic and motor skills — which are sustained until 3 years old — compared with children having siblings with typical development; differences in language skills are larger than those in motor skills.3 The disease heritability is estimated at around 50% to 95%. Indeed ASD is one of the most heritable neuropsychiatric disorders.4 Many of the known ASD variants are located in genes which ultimately control synaptic plasticity. However, most ASD-associated genetic variants account for less than 1% of cases. Nevertheless, genome-wide testing might be of interest for a given child. In fact, for some variants, sufficient data exist to predict developmental outcome and provide anticipatory care for known medical comorbidities (see Fernandez and Scherer in this issue, p 353).

Manzini et al (in this issue, p 335) provide an overview of the current state of ASD genetics and of how genetic research has increased the development of in vivo and in vitro models using animal and patient cells to evaluate the impact of genetic mutations on cellular function and ultimately on the disease. The next step will be to translate these findings into successful therapies.

Autism-specific brain imaging features have been reported as early as 6 months of age, and age-specific brain changes have been demonstrated across the first 2 years of life. Interestingly, early brain imaging in the first year seems promising for presymptomatic prediction of ASD (Shen and Piven, in this issue p 325).

Treatment for ASD is often multimodal, and includes, among other interventions, early intensive behavior therapy, speech therapy, occupational and physical therapy, social skills training, special education, and vocational training. Early behavior interventions often improve functioning and outcome. There are currently no medications approved for the management of core symptoms of ASD; however, there is some evidence for clinical efficacy of pharmacological treatment when associated symptoms such as irritability (antipsychotics) and hyperactivity (psychostimulants might be of interest) are considered (Stepanova et al, in this issue p 395). Antidepressants may reduce anxiety and compulsions; however, there is little evidence to support their use in ASD. Further research on the safety and efficacy of existing psychotropic medications in ASD is clearly needed, as well as the development of new treatment modalities, especially for core symptoms of ASD.