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Since autism is a spectrum of neurological disorders and developmental problems, symptoms can vary widely between individuals. The severity of autism symptoms can range from mild impairment to extreme disability. Symptoms of ASD also vary with age, manifesting differently in infants, toddlers, older children, adolescents, and adults.
The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) lays out criteria for diagnosing autism spectrum disorder in two areas:
Many treatments have proven to be effective at improving outcomes for people with autism. Read more about autism treatments.
Social and communication problems
Early symptoms of autism in babies may include:
As the child ages, social and language progress may be delayed, or the child may lose social and language skills previously acquired. Children with autism may:
By adolescence and adulthood, people with autism have likely learned to compensate for some social and communication deficits. Still, others may notice:
Repetitive and restricted behaviors
Patterns of repetitive behaviors and restricted interests and activities are a hallmark of autism. Many repetitive behaviors are a form of self-stimulatory behavior, or “stimming.” For people with ASD, stimming can provide calm or comfort in a stressful or overstimulating environment or help focus attention. Repetitive patterns can take many forms, including:
In addition to problems with communication and social and repetitive behaviors, many people with autism experience general symptoms.
Approximately one-third of autistic people have intellectual disabilities, while others have average or significantly above-average intellectual abilities.
Cognitive patterns that display rigid or literal thinking are common in people with autism. Children with ASD may lack awareness or fear of danger. Others may interpret people with autism as lacking in “common sense.”
Sleep issues are extremely common in people with autism, perhaps as high as 80 percent. People with ASD may have trouble getting to sleep, wake up repeatedly during the night, or wake very early in the morning. Autism symptoms such as anxiety or gastrointestinal discomfort may contribute to sleep difficulties. Side effects of medications can also make it hard to sleep. Insufficient sleep can exacerbate learning difficulties, hyperactivity, and problematic behavior.
Approximately 45 percent of children with ASD experience gastrointestinal (GI) problems such as recurring diarrhea, constipation, and abdominal pain. There is some evidence that the makeup of intestinal bacteria may differ between people who have autism and people who do not. It is also noteworthy that 36 percent of children with ASD have food allergies, while only between 5 and 8 percent of children without autism do. More research is needed to determine the relationship between autism and GI issues.
Moderate to severe loss of muscle tone occurs in approximately 30 percent of autistic children. Low muscle tone can contribute to clumsiness and problems with gross and fine motor skills, which are also common in those with ASD.
Common coexisting conditions
Certain neurological and psychological conditions are more prevalent in those with autism than in the general population. Scientists theorize that some of these conditions may involve changes in the same genes implicated in the development of autism.
Sensory processing disorder (SPD)
Research indicates that as many as 75 percent of autistic children also have SPD.
Previously known as sensory integration dysfunction (SID), SPD makes it difficult for people to correctly receive and interpret sensory information and act upon it appropriately.
Attention-deficit/hyperactivity disorder (ADHD)
Researchers estimate that half of children with autism also have ADHD, which causes inattention, hyperactivity, or both.
Approximately 30 percent of children with ASD have pica, a craving to eat non-food items such as dirt, sand, paint, ice, or hair.
Approximately one-third of people on the autism spectrum also have epilepsy. In children on the spectrum, intellectual disability increases the risk for developing epilepsy. An estimated 20 percent of autistic children with an intellectual disability develop epilepsy, while 8 percent of those without intellectual problems begin having seizures. In people with autism, seizures most commonly start either in preschool or adolescence.
Hearing and visual impairments
Autism disorder is diagnosed in about 30 percent of children who receive educational services related to hearing or visual impairment.
Obsessive-compulsive disorder (OCD)
According to one study, 17 percent of children with autism also have symptoms of OCD.
Problems with anxiety, including phobias and panic disorders, are common among people with autism.
Do symptoms of autism differ between boys and girls?
According to one study involving 800 children with autistic spectrum disorder, girls with autism often exhibit different symptoms from those seen in boys. Specifically, girls are less likely to display repetitive and restrictive behaviors. The study found that social and communication deficits were equally prevalent between boys and girls. Other researchers theorize that social and communication challenges are more subtle in girls, with girls being less likely to act out and more likely to smile, make eye contact, and mimic others’ behavior to fit in. Girls with ASD may simply be thought shy or lacking in self-confidence. Girls are often misdiagnosed or diagnosed much later than boys. Since health professionals expect boys to have autism at much higher rates than girls, they may be less likely to consider ASD as a diagnosis for a girl.