[TheMercenary]

Frequency
United States
Autistic disorder and related conditions affect up to 10-20 individuals per 10,000 population. Estimates of the prevalence of autism suggest that as many as 400,000 individuals in the United States have autism and related conditions. Autism spectrum disorder is one of the most common childhood developmental disabilities. Current epidemiological studies are needed to identify the incidence, prevalence, and distribution of autistic disorder in the United States.

Epidemiological studies of relatively uncommon conditions such as autism spectrum disorders are expensive. A suitable strategy is the performance of multiple screenings on a population, each time identifying more likely subjects for detailed investigation. For example, a checklist such as the Autism Screening Checklist can be distributed to all parents and guardians of a target population. The Autism Screening Checklist identifies those children with characteristics of autism spectrum disorders. It differentiates children with autism spectrum disorders from children with schizophrenia and other psychoses. The higher the score on the Autism Screening Checklist (see Media file 1 for a printable version), the more likely the presence of autism spectrum disorders.


International
Autistic disorder and related conditions affect up to 10-15 people per 10,000 population. Studies in Japan report much higher rates.12 Japanese investigators suggest that these findings reflect the careful evaluations performed by Japanese clinicians. Some studies suggest that infectious diseases that are prevalent in parts of Japan may account for higher rates of autistic disorder. Epidemiologic studies are needed to assess the current incidence, prevalence, and distribution of autistic disorder throughout the world. These studies may help focus on causality.

Mortality/Morbidity
The long-term outcome for individuals with autistic disorder is directly proportional to the IQ of individuals. In other words, individuals with autistic disorder and intellectual limitations have poorer outcomes. Individuals with autistic disorder and profound mental retardation may require constant care in a residential treatment facility.

Race
Japanese studies often indicate the more common occurrence of autism in Japan than in other countries.12 The high rates of autism reported in many Japanese studies may reflect higher incidence and prevalence in Japan. Alternatively, because Japanese clinicians are highly skilled to diagnose autism, they may identify cases that are overlooked in other countries. Some studies suggest that some cases of autism in Japan result from GI infections and other infections due to the ingestion of seafood and other aquatic sources of food characteristic of Japan.

Sex
The male-to-female ratio is 3-4:1.
Autistic disorder is most common in boys who have the 46,XY karyotype (ie, the karyotype of healthy normal boys). In some studies, fragile X is reported in approximately one tenth of males with autistic disorder.13,14,15,16,17,18
Age
Autistic disorder manifests in early childhood. Using contemporary criteria, the absence of abnormalities in the first 30 months of life rules out autistic disorder. For information about individuals with later onset of symptoms consistent with autistic disorder, see Pervasive Developmental Disorder: Childhood Disintegration Disorder, Pervasive Developmental Disorder: Rett Syndrome, Pervasive Developmental Disorder: Asperger Syndrome, and Pervasive Developmental Disorder (not otherwise specified).
Many parents report normal development in their child until age 2 years before noticing the deficits in social and communicative skills.
Individuals with autism spectrum disorder and unspecified pervasive developmental disorder typically benefit from behaviorally oriented therapeutic programs developed specifically for people with autistic disorder. Therefore, children who manifest symptoms of autistic disorder, other pervasive developmental disorders, and other autism spectrum disorders are likely to benefit from the highly specialized intensive intervention programs designed for children with these disorders.
Because optimal results occur when intensive interventions are administered early in childhood, autistic children should be placed in specialized programs as soon as the diagnosis is entertained. Delays in placement of a young child in a specialized program for children with autistic disorder may reduce the effectiveness of those interventions. Parents, pediatricians, other health care providers, and educators are advised to seek the assistance of people who are familiar with early intervention programs for children with autistic disorder. The Autism Society of America can help parents obtain appropriate referrals for optimal interventions.
Clinical
History
Environmental exposures: Roberts and colleagues (2007) and Samson (2007) have reported that women in the Central Valley of California who were exposed to endosulfan and dicofol, organochlorine pesticides, during the first trimester of pregnancy were more likely to have children with autism spectrum disorders.7,8 Thus, obstetricians and other health workers can wisely advise women who are likely to become pregnant to avoid contact with pesticides and other environmental contaminants.
Protodeclarative pointing
Protodeclarative pointing is the use of the index finger to indicate an item of interest to another person. Toddlers typically learn to use protodeclarative pointing to communicate their concern for an object to others.
The absence of protodeclarative pointing is predictive of the later diagnosis of autism. The presence of protodeclarative pointing can be assessed by interview of the parent or caregiver. As a screening question, Baron-Cohen and colleagues (1992, 1996) have demonstrated that the absence of a positive response to an inquiry about protodeclarative pointing is predictive of the later diagnosis of autism.19,20 Screening questions include "Does your child ever use his or her index finger to point, to indicate interest in something?" The absence of a positive response to this question suggests the need for a specialized assessment for possible pervasive developmental disorder.
Environmental stimuli
Parents report unusual responses to environmental stimuli, including excessive reaction or an unexpected lack of reaction to sensory input.
Sounds, such as vacuum cleaners or motorcycles, may elicit incessant screaming from a child with autistic disorder. Playing a radio, phonograph, or television at a loud level may appear to produce auditory stimulation of a painful magnitude. Sometimes parents must rearrange the family routine so that the child is absent during noisy housekeeping activities.
Children with autistic disorder may also display exaggerated responses or rage to everyday sensory stimuli, such as bright lights or touching.