Classic autism
Classic autism—also known as childhood autism, autistic disorder, or Kanner's syndrome—is a formerly diagnosed neurodevelopmental disorder first described by Leo Kanner in 1943. It is characterized by atypical and impaired development in social interaction and communication as well as restricted and repetitive behaviors, activities, and interests. These symptoms first appear in early childhood and persist throughout life.
Classic autism was last recognized as a diagnosis in the DSM-IV and ICD-10, and has been superseded by autism-spectrum disorder in the DSM-5 and ICD-11. Globally, classic autism was estimated to affect 24.8 million people as of 2015.
Autism is likely caused by a combination of genetic and environmental factors, with genetic factors thought to heavily predominate. Certain proposed environmental causes of autism have been met with controversy, such as the fraudulent vaccine hypothesis that, although disproved, has negatively impacted vaccination rates among children.
Since the DSM-5/ICD-11, the term "autism" more commonly refers to the broader autism spectrum.
Characteristics
Autism is a highly variable neurodevelopmental disorder whose symptoms first appear during infancy or childhood, and generally follow a steady course without remission. Autistic people may be severely impaired in some respects but average, or even superior, in others. Overt symptoms gradually begin after the age of six months and become established by age two or three years. Some autistic children experience regression in their communication and social skills after reaching developmental milestones at a normal pace. It was said to be distinguished by a characteristic triad of symptoms: impairments in social interaction, impairments in communication, and repetitive behavior. Other aspects, such as atypical eating, are also common but are not essential for diagnosis. Individual symptoms of autism occur in the general population and appear not to highly be associated, without a sharp line separating pathologically severe from common traits.Social development
Autistic people have social impairments and often lack the intuition about others that many people take for granted. Unusual social development becomes apparent early in childhood. Autistic infants show less attention to social stimuli, smile and look at others less often, and respond less to their own name. Autistic toddlers differ more strikingly from social norms; for example, they have less eye contact and turn-taking, and do not have the ability to use simple movements to express themselves, such as pointing at things. Three- to five-year-old autistic children are less likely to exhibit social understanding, approach others spontaneously, imitate and respond to emotions, communicate nonverbally, and take turns with others. However, they do form attachments to their primary caregivers. Most autistic children displayed moderately less attachment security than neurotypical children, although this difference disappears in children with higher mental development or less pronounced autistic traits. Children with high-functioning autism have more intense and frequent loneliness compared to non-autistic peers, despite the common belief that autistic children prefer to be alone. Making and maintaining friendships often proves to be difficult for autistic people. For them, the quality of friendships, not the number of friends, predicts how lonely they feel. Functional friendships, such as those resulting in invitations to parties, may affect the quality of life more deeply.Communication
Differences in communication may be present from the first year of life, and may include delayed onset of babbling, unusual gestures, diminished responsiveness, and vocal patterns that are not synchronized with the caregiver. In the second and third years, autistic children have less frequent and less diverse babbling, consonants, words, and word combinations; their gestures are less often integrated with words. Autistic children are less likely to make requests or share experiences, and are more likely to simply repeat others' words or reverse pronouns. Deficits in joint attention may be present — for example, they may look at a pointing hand instead of the object to which the hand is pointing. Autistic children may have difficulty with imaginative play and with developing symbols into language. It is also thought that autistic and non-autistic adults produce different facial expressions, and that these differences could contribute to bidirectional communication difficulties.Repetitive behavior
Autistic individuals can display many forms of repetitive or restricted behavior, which the Repetitive Behavior Scale-Revised categorizes as follows.- Stereotyped behaviors: Repetitive movements, such as hand flapping, head rolling, or body rocking.
- Compulsive behaviors: Time-consuming behaviors intended to reduce the anxiety that an individual feels compelled to perform repeatedly or according to rigid rules, such as placing objects in a specific order, checking things, or handwashing.
- Sameness: Resistance to change; for example, insisting that the furniture not be moved or refusing to be interrupted.
- Ritualistic behavior: Unvarying pattern of daily activities, such as an unchanging menu or a dressing ritual.
- Restricted interests: Interests or fixations that are abnormal in theme or intensity of focus, such as preoccupation with a single television program, toy, or game.
Other symptoms
Autistic individuals may have symptoms that are independent of the diagnosis. An estimated 0.5% to 10% of individuals with classic autism show unusual abilities, ranging from splinter skills such as the memorization of trivia to the extraordinarily rare talents of prodigious autistic savants. Sensory abnormalities are found in over 90% of autistic people, and are considered core features by some, although there is no good evidence that sensory symptoms differentiate autism from other developmental disorders. An estimated 60–80% of autistic people have motor signs that include poor muscle tone, poor motor planning, and toe walking.Causes
It was presumed initially that there was a common cause at the genetic, cognitive, and neural levels for classic autism's characteristic triad of symptoms. However, over time, there was increasing evidence that autism was instead a complex and highly heritable disorder whose core aspects have distinct causes which often co-occur.The exact causes of autism are unknown, but it is believed that both genetic and environmental factors play a role in its development. Multiple studies have shown structural and functional atypicalities in the brains of autistic people. Experiments have been conducted to determine if the degree of brain atypicality yields any correlation to the severity of autism. One study done by Elia et al. used magnetic resonance imaging on the midsagittal area of the cerebrum, midbrain, cerebellar vermis, corpus callosum, and vermal lobules VI and VII to measure brain atypicalities in children with low-functioning autism. The results suggested that the midbrain structures correlate with certain developmental behavioral aspects such as motivation, mnemonic, and learning processes, though there is more research needed to confirm this. Furthermore, many developmental processes may contribute to several types of brain atypicalities in autism; therefore, determining the link between such atypicalities and severity of autism proves difficult.
Although theories regarding vaccines lack convincing scientific evidence, are biologically implausible, and originated from a fraudulent study, parental concern about a potential vaccine link with autism has led to lower rates of childhood immunizations, outbreaks of previously controlled childhood diseases in some countries, and the preventable deaths of several children.
Diagnosis
of classic autism was based on behavioral symptoms, not cause or mechanism.The ICD-10 criteria for childhood autism postulate that abnormal or impaired development is evident before the age of 3 in receptive or expressive language used in social communication, development of selective social attachments or reciprocal social interactions, or functional and symbolic play. The children would also be required to exhibit six other symptoms from three macro-categories pertaining to qualitative impairment in social interactions, quantitative abnormalities in communication, and restricted/repetitive/stereotyped patterns of behavior, interests, and activities. ICD-10 differentiates high functioning and low-functioning autistic people by diagnosing the additional code of intellectual disability.
Classification
Classic autism was listed as autistic disorder in the fourth edition of the American Psychiatric Association's diagnostic manual, as one of the five pervasive developmental disorders. However, the PDDs were collapsed into the single diagnosis of Autism Spectrum Disorder in 2013, and the WHO's diagnostic manual ICD-11 followed suit a few years later. Classic autism was said to be characterized by widespread abnormalities of social interactions and communication, severely restricted interests, and highly repetitive behavior.Of the PDDs, Asperger syndrome was closest to classic autism in signs and likely causes; Rett syndrome and childhood disintegrative disorder share several signs with it, but were understood to potentially have unrelated causes; PDD not otherwise specified was diagnosed when the criteria were not met for one of the other four PDDs. People would usually attract a diagnosis of Asperger syndrome rather than classic autism if they showed no substantial delay in language development, but early language ability was found to be a poor predictor of outcomes in adulthood.