Autism spectrum disorder is also defined by restricted, repetitive patterns of behavior, interests, or activities (as specified in Criterion B), which show a range of manifestations according to age and ability, intervention, and current supports. Stereotyped or repetitive behaviors include simple motor stereotypies (e.g., hand ﬂapping, finger ﬂicking), repeti- tive use of objects (e.g., spinning coins, lining up toys), and repetitive speech (e.g., echola- lia, the delayed or immediate parroting of heard words; use of "you" when referring to self; stereotyped use of words, phrases, or prosodic patterns). Excessive adherence to rou- tines and restricted patterns of behavior may be manifest in resistance to change (e.g., dis- tress at apparently small changes, such as in packaging of a favorite food; insistence on adherence to rules; rigidity of thinking) or ritualized patterns of verbal or nonverbal be- havior (e.g., repetitive questioning, pacing a perimeter). Highly restricted, fixated interests in autism spectrum disorder tend to be abnormal in intensity or focus (e.g., a toddler strongly attached to a pan; a child preoccupied with vacuum cleaners; an adult spending hours writing out timetables). Some fascinations and routines may relate to apparent hy- per- or hyporeactivity to sensory input, manifested through extreme responses to specific sounds or textures, excessive smelling or touching of objects, fascination with lights or spinning objects, and sometimes apparent indifference to pain, heat, or cold. Extreme re- action to or rituals involving taste, smell, texture, or appearance of food or excessive food restrictions are common and may be a presenting feature of autism spectrum disorder.
Many adults with autism spectrum disorder without intellectual or language disabili- ties learn to suppress repetitive behavior in public. Special interests may be a source of pleasure and motivation and provide avenues for education and employment later in life.
Diagnostic criteria may be met when restricted, repetitive patterns of behavior, interests, or activities were clearly present during childhood or at some time in the past, even if symptoms are no longer present.
Criterion D requires that the features must cause clinically significant impairment in so- cial, occupational, or other important areas of current functioning. Criterion E specifies that the social communication deficits, although sometimes accompanied by intellectual disabil- ity (intellectual developmental disorder), are not in line with the individual’s developmental level; impairments exceed difficulties expected on the basis of developmental level.
Standardized behavioral diagnostic instruments with good psychometric properties, including caregiver interviews, questionnaires and clinician observation measures, are available and can improve reliability of diagnosis over time and across clinicians.
Many individuals with autism spectrum disorder also have intellectual impairment and/ or language impairment (e.g., slow to talk, language comprehension behind production). Even those with average or high intelligence have an uneven profile of abilities. The gap between intellectual and adaptive functional skills is often large. Motor deficits are often present, in- cluding odd gait, clumsiness, and other abnormal motor signs (e.g., walking on tiptoes). Self- injury (e.g., head banging, biting the wrist) may occur, and disruptive/challenging behav- iors are more common in children and adolescents with autism spectrum disorder than other disorders, including intellectual disability. Adolescents and adults with autism spec- trum disorder are prone to anxiety and depression. Some individuals develop catatonic—like motor behavior (slowing and ”freezing” mid-action), but these are typically not of the mag- nitude of a catatonic episode. However, it is possible for individuals with autism spectrum disorder to experience a marked deterioration in motor symptoms and display a full cata- tonic episode with symptoms such as mutism, posturing, grimacing and waxy ﬂexibility.
The risk period for comorbid catatonia appears to be greatest in the adolescent years.
In recent years, reported frequencies for autism spectrum disorder across US. and non-