The previous classification of four separate disorders, autism, Asperger syndrome, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified, have been combined in the DSM-5 under the category of autism spectrum disorder (ASD; Table 20.1 ). Specifiers of symptom severity in regard to core deficits in the domains of social communication impairments and restricted, repetitive patterns of behavior (RRPB) are also provided. A diagnosis of social (pragmatic) communication disorder (SCD) may be made in the absence of RRPBs.

Onset of ASD is in infancy and preschool years. Hallmarks of ASD include impaired communication and impaired social interaction as well as stereotypical behaviors, interests, and activities. Intellectual disability is common (~38% according to Centers for Disease Control and Prevention [CDC] estimates); although the majority of children demonstrate average to high intelligence scores, they often show uneven abilities.

ASD is seen in approximately 1% of the population with equal prevalence rates among all racial and ethnic groups. Boys appear to be diagnosed much more frequently than girls (4 : 1 ratio); however, girls with the disorder tend to be more severely affected regarding intellectual abilities and symptom severity.

ASD is characterized by lifelong marked impairment in social interaction and social communication in addition to RRPBs. Approximately 20% of parents report relatively normal development until 1-2 years of age, followed by a steady or sudden decline. In infants with ASD there is delayed or absent social smiling. The young child may spend hours in solitary play and be socially withdrawn with indifference to attempts at communication. Patients with autism often are not able to understand nonverbal communication (e.g., eye contact, facial expressions) and do not interact with people as significantly different from objects. Communication and speech often are delayed and, when present, may be marked by echolalia (repetition of language of others), perseveration (prolonged repetition of words or behaviors of others), pronoun reversal, nonsense rhyming, and other abnormalities. Intense absorbing interests, ritualistic behavior, and compulsive routines are characteristic, and their disruption may invoke behavioral dysregulation. Self-injurious behaviors (head banging, biting), repetitive motor mannerisms (rocking, lining up objects, simple motor stereotypies), and hyperreactivity/hyporeactivity to their environment (diminished response to pain, adverse reactions to sounds/textures, or unusual visual inspection of objects) may be noted.

Although the full etiology of ASD is unknown, it is largely considered a genetic disorder. There is an increased risk of ASD in siblings compared to the general population. Twin studies have revealed high levels of concordance (36-95%) for identical twins. Family studies reveal prevalence rates of between 2% and 18% in siblings, and when absent, there may be increased risk for other language, learning, and social development problems.

It has been proposed that brain connectivity is adversely affected. Abnormalities in the limbic system, temporal, and frontal lobes have been suggested. Some postmortem studies reveal abnormalities in the brain microarchitecture, size, and neuronal packing. Functional magnetic resonance imaging (fMRI) studies show that hypoactivity of the fusiform gyrus of the amygdala, a location involved in face processing tasks and facial expression recognition involved in social and affective judgments, may be impacted in ASD.

There are no definitive laboratory studies for ASD, but they can help rule out other diagnoses. A hearing test (may account for the language deficits), chromosomal testing (to identify fragile X syndrome, tubular sclerosis, and genetic polymorphisms), congenital viral infections, and metabolic disorders (phenylketonuria) should be performed. Electroencephalography abnormalities may be seen in 20-25% of children with ASD, but they are not diagnostic.

The American Academy of Pediatrics (AAP) recommends screening for autism at 18 and 24 months of age. There are numerous screening measures that may be employed (e.g., Childhood Autism Rating Scale [CARS], Modified Checklist for Autism in Toddlers [M-CHAT], Gilliam Autism Rating Scale [GARS], and Screening Tool for Autism in Toddlers and Young Children [STAT]) to assist with appropriate referral for diagnostic evaluation. “Gold standard” psychological measures such as the Autism Diagnostic Observation Schedule (ADOS) and Autism Diagnostic Interview (ADI) are commonly recommended to confirm a diagnosis. Other measures of language, adaptive skills, and intelligence may also be administered if ASD is suspected. Psychological tests in children with ASD often show strengths in nonverbal tasks (e.g., puzzles) and marked deficiency in verbal cognitive abilities. Speech pathology consultation can be helpful in evaluating the communication difficulties.

Common psychiatric co-morbidities include intellectual disability, language/communication disorders, anxiety disorders, attention-deficit/hyperactivity disorder, developmental coordination disorder, and depressive disorders. Other medical complexities commonly seen in children with ASD include seizure disorder, sleep disorders, and gastrointestinal disorders (constipation, food selectivity). Intellectual abilities and language abilities are the strongest predictors of improved long-term prognosis. The earliest studies of autism suggested a relatively poor prognosis, with only a small number of individuals (1-2%) being able to function independently as adults. Recent research reveals major gains, but not a cure, with early diagnosis and treatment.

SCD involves difficulties with the social use of verbal and nonverbal communication. SCD involves struggles with using communication for social purposes (e.g., greeting others, sharing information, conversational rules, inferences, and pragmatic skills). SCD is marked by many of the same communication deficits seen in children with ASD with the absence of RRPBs. SCD is believed to be rare in children prior to 4 years of age; however, the prevalence rate is unclear because of its recent addition to the DSM-5. Typically, speech and language therapy and social skills training are employed to treat SCD.

Treatment of ASD is typically multimodal. At present, there are no pharmacological treatments for the core symptoms of ASDs. Antipsychotics (risperidone, olanzapine, quetiapine, aripiprazole, ziprasidone, paliperidone, haloperidol, thioridazine) are used for aggression, agitation, irritability, hyperactivity, and self-injurious behavior. Anticonvulsants have also been used for aggression. Naltrexone has been used to decrease self-injurious behavior, presumably by blocking endogenous opioids. Selective serotonin reuptake inhibitors are given for anxiety, perseveration, compulsions, depression, and social isolation. Stimulants are useful for hyperactivity and inattention; however, there are reports of significant worsening of irritability and aggression in some patients treated with stimulants. Alpha-2 agonists (guanfacine, clonidine) are used for hyperactivity, aggression, and sleep dysregulation, although melatonin is first-line medication for sleep dysregulation.

A variety of nonpharmacological interventions exist for ASD. Such interventions have largely fallen under the classification of behavioral training. Models have typically employed therapies individually tailored for children with ASD and their families/caregivers. Evidence suggests that useful therapies have included techniques from applied behavior analysis (ABA), discrete trial training (DTT), functional behavioral analysis (FBA), and structured teaching (TEACCH Model). Behavioral management training for parents has also demonstrated efficacy in helping with unwanted behaviors. Special education services should be individualized for the child. Occupational, speech, and physical therapy are often required. Referral for disability services and support is often warranted. Family support groups and individual supportive counseling for parents is useful. The prognosis for ASD is guarded and varies greatly from child to child. There are no known methods of primary prevention. Treatment and educational interventions are aimed at decreasing morbidity and maximizing function.