Autism is a disorder that affects how the brain grows and the child functions in the first years of life. The characteristic features of autism include lack of social engagements, use of language and poor playing ability with other children. Some children begin showing signs of autism around their first birthday, while others lose previously acquired skills in their toddler years. Together, autism results in missed developmental milestones and often lasts throughout the lifetime.

According to the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM-5), an autism diagnosis involves challenges in the following two areas:

1. Social interactions and communications
2. Restricted, repetitive patterns of behavior and interests

The range and degree of autism symptoms falls on a continuum, called the autism spectrum. Therefore, both children with severe deficits as well as those who are mildly affected are considered to have Autism Spectrum Disorder (ASD).

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Many causes can contribute to autism. Researchers in the last several years have identified different types of genetic and environmental factors associated with this disorder. Scientists largely agree that these risk factors mediate abnormal brain development that ultimately leads to autism. But no one really knows how the risk factors contribute to the changes in brain structure or function to cause Autism Spectrum Disorder (ASD).

Researchers are conducting extensive studies to determine how differences in brain development associate with autism characteristics. Many of the studies focus on neurons, a type of cell that can send electric and chemical signals in the central nervous system. The brain uses neurons to process and respond to information received from our five senses: sight, sound, touch, hearing, and taste. Based on these experiments, researchers have developed several theories about autism:

1. There are too many connections between neurons in certain brain regions.
2. Neurons do not move to the right layers of the brain during fetal development.
3. Neurons have an imbalance between their on/off states and emit signals either too frequently or not enough.
4. A part of the neuron, called the synapse, that is required for sending and receiving signals does not form properly in autism.

The factors that may contribute to these problems-such as the immune system, cell function, genetic predisposition, and the environment-are even less well understood. The fact that ASD can appear so different between individuals suggests that multiple paths to ASD exist, each path ending in a slightly different set or severity of traits.

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At this stage in autism research, we still do not have concrete answers to tell us who will get autism. However, there is a strong consensus in the research community that autism results from environmental triggers combined with a person's particular DNA code.

Some studies have linked an increased age of the father, maternal infection, toxic exposures, or even nutritional inadequacies during pregnancy to the onset of autism. While some of these factors do increase risk, they do not guarantee that a child will develop autism.

Signs that a child has autism can begin as early as three months of age, but many children are not diagnosed until four years of age or older. Because there is no way to determine who will or won't develop autism to date, many hospitals offer autism screening questionnaires around two years of age. To learn more about autism screening, please visit here.

If you would like to read more about autism risk factors, we invite you to explore our Risk Factors topic pages here.

Several conditions, known as risk factors, have been linked to an increased likelihood of developing ASD. Risk factors can be genetic or environmental.

Genetic risk factors relate to errors in our DNA, which means they are present at birth. Genetics play a strong role in the development of Autism Spectrum Disorders (ASDs). Autism is shared among 50 to 70 percent of identical twins, compared with zero to 10 percent of fraternal twins.

Environmental risk factors, however, stem from social, physical, or chemical exposures and can be present during fetal development or months to years after birth. The environmental causes of autism are fiercely debated and extremely controversial. With the exception of a few seldom-used teratogenic drugs, specific environmental factors are linked to autism by association, not causation, and few such factors have been rigorously tested. However, there is compelling evidence that environmental exposures can contribute to neurodevelopmental disorders.

The scientific literature has associated numerous environmental factors with autism. Currently, environmental factors as diverse as parental factors, obstetric complications, vitamin deficiencies, exposures to drugs and environmental contaminants, immune challenge, and socio-economic status have been implicated in autism.

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No genetic testing is currently available for the diagnosis of autism. Autism is diagnosed by behavioral observations of core deficits by trained professionals according to the guidelines established by the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM-5).

However, some genetic tests can guide ASD medical management. At present, these tests can identify a genetic risk factor in 15 to 20 percent of ASD individuals that undergo testing. New techniques, such as next generation sequencing (NGS) and chromosomal microarray analysis (CMA), show promising results for identifying genetic causes in a larger percentage of ASD individuals because of their ability to analyze DNA at higher resolution.

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Previous studies of autism recurrence-when a second child has ASD-indicate a wide range of likelihood. In a population-based study, researchers observed ASD recurrence rates in full- and half-siblings. The research team used records for all children, about 1.5 million, born in Denmark between January 1, 1980 and December 31, 2004.

The researchers reported an overall recurrence risk for full-siblings of seven percent. This means that for every 100 families with autism, seven of those families will have a second child with autism. This study indicates a somewhat lower rate of recurrence than previously reported, a valuable finding for parents.

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Many children with autism have symptoms beyond social, language, and motor. Some of these conditions include sleep disorders, gastrointestinal complaints, epilepsy, cranial anomalies, muscular dystrophies, and other mental disorders.

In 2012, researchers surveyed associated conditions in more than 14,000 individuals 35 years of age or younger. The research team identified the prevalence of the following conditions in children and young adults with autism:

• epilepsy (19.4%)
• head anomalies (12.4%)
• bowel disorders (11.7%)
• schizophrenia (2.4%)
• sleeping disorders (1.1%)
• Down syndrome (0.9%)
• tuberous sclerosis (0.8%)
• inflammatory bowel disease (IBD) (0.8%)
• autoimmune disorders (DM1) (0.7%)
• fragile X syndrome (0.5%)

Other conditions sometimes co-diagnosed with autism, but not covered in the above study, include ADHD, irritability, Rett Syndrome, Angelman syndrome, and Dravet's syndrome.

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The latest CDC reports indicate that about one in 68 children have autism. Boys are at higher risk for autism, with nearly one in 42 boys receiving an autism diagnosis, compared to one in 189 girls. The high prevalence of autism is of major public concern. Increased autism prevalence over previous decades has fueled major scientific research interests and news media focus.

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If you think your child might have autism, you can go to your health care provider for evaluation. To date, trained clinicians diagnose autism following guidelines set forth by the American Psychiatric Association.

There are two stages for diagnosing autism:

1. The first stage is screening, an easy-to-use, general method that identifies a potential risk for developing autism.
2. The second stage is diagnostics, an in-depth examination that requires the assessment of cognition, linguistics, and motor skills by a qualified medical team to accurately diagnose the developmental disorder and the degree of the disorder.

A multidisciplinary approach that incorporates clinical evaluations and behavioral observations has been the gold standard for autism diagnosis.

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If your child does not meet the criteria for Autism Spectrum Disorder, the clinician may evaluate your child for social communication disorder. Other diagnoses that resemble some of the characteristics of autism include specific language disorders, developmental delay, attention deficit hyperactivity disorder, mood and anxiety disorders, obsessive-compulsive disorder, and several syndromic disorders, such as Rett syndrome. Your doctor may also test your child for hearing impairment, visual impairment, or selective mutism.

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The range and degree of autism symptoms falls on a continuum, called the autism spectrum. Therefore, both children with severe deficits as well as those who are mildly affected are considered to have Autism Spectrum Disorder (ASD).

There are several co-occurring symptoms in autism. These symptoms range in presentation and severity. Children with autism frequently have an intellectual disability, but some children with autism will have normal intelligence. Children with autism may also have seizures, motor abnormalities, anxiety, sleep cycle disturbances, gastrointestinal problems, immune dysfunction and sensory disturbances. Not all the features are present in every child. Instead, a subset of features underlies autism in each individual.

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Between 3 and 25 percent of children diagnosed with autism who are given extensive behavioral intervention can progress sufficiently to enter the typical range of social and cognitive abilities.

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There is no known cure for autism. Many websites on the Internet claim to reveal the cause of autism or promise a cure. Unfortunately, a lot of these claims are not from evidence-based research, and some may even be harmful.

A recent scientific study has documented optimal outcome for a group of individuals with autism who have "outgrown" their autism diagnosis (Fien, et al, 2013). Much research is needed to understand how and who will have the optimal outcome in ASD.

There are several therapy options that can help a child with autism enter a typical range of social and cognitive abilities. Behavioral therapies, especially Applied Behavioral Analysis (ABA) and Early Start Denver Model (ESDM), have shown promising results. Additionally, doctors may prescribe pharmaceutical interventions, such as antidepressant medications, to help with commonly associated symptoms.

Reference: Fein D, Barton M, Eigsti IM, Kelley E, Naigles L, Schultz RT, Stevens M, Helt M, Orinstein A, Rosenthal M, Troyb E, Tysons K. (2013). Optimal outcome in individuals with a history of autism. J child Psychol Psychiatry, 54(2):195-205.

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Doctors have autism screening tools for toddlers as young as 18 months of age. A well-known screening tool is the Modified Checklist for Autism in Toddlers (M-CHAT).
M-CHAT is a list of 23 yes-or-no questions about a child's usual behavior for parents of 16- to 30-month-old children. If M-CHAT is used on children younger or older than the age range on which it was validated, or if someone other than the child's parent completes the M-CHAT, the results may not be valid.

The primary goal of the M-CHAT is to maximize sensitivity, meaning to identify as many potential cases of Autism Spectrum Disorder (ASD) as possible. For this reason, M-CHAT tends to have a high false-positive rate (not all children who are found to be at risk for developing ASD using M-CHAT will go on to be diagnosed with ASD). To reduce the false-positive rate, a follow-up interview is suggested.

A 2013 study found that the updated version of the M-CHAT (M-CHAT, Revised with Follow-up) is better at detecting ASD than its previous iteration. At the same time, the newer version of the screening tool classifies a smaller proportion of children as high- or medium-risk-reducing the number of families who would need to pursue follow-up testing.

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According to the Autism Speaks website, "the National Research Council recommends that, during the preschool period, children with autism should receive approximately 25 hours of structured intervention per week."

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There are several therapy options, including:

• Parent-delivered programs
• Developmental programs
• Occupational programs
• Speech-language therapy
• Small group or 1:1 programs

Check out these other resources for more information about autism therapies.

Targeted intervention can be beneficial for a child of any age. If you think your child may have autism, several screening and diagnostic tools are designed for older children. Four commonly used tools are outlined below:

The Social Communication Questionnaire (SCQ) is a parental questionnaire with 40 yes-or-no items. Two forms of the questionnaire are used: current and lifetime. The questionnaire takes less than 10 minutes, and scoring involves a total score with cutoff points. The SCQ is designed for individuals over 4 years of age, with a mental age over 2 years. SCQ is a quick and inexpensive way to routinely screen for Autism Spectrum Disorder (ASD).

The Autism Spectrum Screening Questionnaire (ASSQ) is a 27-item, yes/somewhat/no-style questionnaire meant to assess the symptoms characteristic of high-functioning Autism Spectrum Disorders in children and adolescents. A parent, teacher, or other lay person who knows the child being screened can complete the checklist. Optimal cutoff scores have already been established for the ASSQ to minimize the number of false positives while retaining a high level of ASD identification. ASSQ is an easy, inexpensive, and well-tested screening device for the detection of ASDs.

The Childhood Autism Spectrum Test (CAST), also known as the Childhood Asperger Screening Test, detects Autism Spectrum Disorders (ASDs) in 5- to 11-year-old children by using a parental questionnaire to measure social and communication skills. The CAST questionnaire contains 37 yes-or-no questions about the child's social behaviors and communication tendencies. It also contains a separate special needs section that asks about other disorders that the child might have, for example hyperactivity or a physical disability.

The Autism Diagnostic Interview-Revised (ADI-R) is a 100-item interview that helps diagnose autism in children and adults with a mental age over two years. In most cases, the interview lasts for 1.5 to 2.5 hours, including scoring.

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The Food and Drug Administration (FDA) has not approved any medications for the core manifestations of ASD. However, FDA has approved two drugs for treating "irritability" associated with autism.

Often, physicians can offer relief with certain drugs prescribed in an "off-label" manner. "Off-label" is a term used in the medical community for certain FDA-approved drugs that are prescribed and used for conditions for which they were not originally intended but have therapeutic properties for other diseases.

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