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The diagnosis of autism is based on a person's reported and directly observed behavior. [1] There are no known biomarkers for autism spectrum conditions that allow for a conclusive diagnosis. [2]
In most cases, diagnostic criteria codified in the World Health Organization's International Classification of Diseases (ICD) or the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM) are used. These reference manuals are regularly updated based on advances in research, systematic evaluation of clinical experience, and healthcare considerations. Currently, the DSM-5 published in 2013 and the ICD-10 that came into effect in 1994 are used, with the latter in the process of being replaced by the ICD-11 that came into effect in 2022 and is now implemented by healthcare systems across the world. Which autism spectrum diagnoses can be made and which criteria are used depends on the local healthcare system's regulations.
According to the DSM-5-TR (2022), in order to receive a diagnosis of autism spectrum disorder, one must present with "persistent deficits in social communication and social interaction" and "restricted, repetitive patterns of behavior, interests, or activities." [3] These behaviors must begin in early childhood and affect one's ability to perform everyday tasks. Furthermore, the symptoms must not be fully explainable by intellectual developmental disorder or global developmental delay.
There are several factors that make autism spectrum disorder difficult to diagnose. First off, there are no standardized imaging, molecular or genetic tests that can be used to diagnose ASD. [4] Additionally, there is a lot of variety in how ASD affects individuals. The behavioral manifestations of ASD depend on one's developmental stage, age of presentation, current support, and individual variability. [5] [3] Lastly, there are multiple conditions that may present similarly to autism spectrum disorder, including intellectual disability, hearing impairment, a specific language impairment [6] such as Landau–Kleffner syndrome, [7] ADHD, anxiety disorder, and psychotic disorders. [8] Furthermore, the presence of autism can make it harder to diagnose coexisting psychiatric disorders such as depression. [9] Diagnosing will be much harder in adults, since most people with ASD who reach adulthood undiagnosed, learn diverse (and often intense) masking techniques which make external diagnosis almost impossible.
The DSM-5-TR criteria lists 5 criteria (with examples) which include 2 groups of criteria (the first two): [3]
Ideally the diagnosis of ASD should be given by a team of clinicians (e.g. pediatricians, child psychiatrists, child neurologists) based on information provided from the affected individual, caregivers, other medical professionals and from direct observation. [10] Evaluation of a child or adult for autism spectrum disorder typically starts with a pediatrician or primary care physician taking a developmental history and performing a physical exam. If warranted, the physician may refer the individual to an ASD specialist who will observe and assess cognitive, communication, family, and other factors using standardized tools, and taking into account any associated medical conditions. [6] A pediatric neuropsychologist is often asked to assess behavior and cognitive skills, both to aid diagnosis and to help recommend educational interventions. [11] Further workup may be performed after someone is diagnosed with ASD. This may include a clinical genetics evaluation particularly when other symptoms already suggest a genetic cause. [12] Although up to 40% of ASD cases may be linked to genetic causes, [13] it is not currently recommended to perform complete genetic testing on every individual who is diagnosed with ASD. Consensus guidelines for genetic testing in patients with ASD in the US and UK are limited to high-resolution chromosome and fragile X testing. [12] Metabolic and neuroimaging tests are also not routinely performed for diagnosis of ASD. [12]
The age at which ASD is diagnosed varies. Sometimes ASD can be diagnosed as early as 18 months, however, diagnosis of ASD before the age of two years may not be reliable. [4] Diagnosis becomes increasingly stable over the first three years of life. For example, a one-year-old who meets diagnostic criteria for ASD is less likely than a three-year-old to continue to do so a few years later. [14] Additionally, age of diagnosis may depend on the severity of ASD, with more severe forms of ASD more likely to be diagnosed at an earlier age. [15] Issues with access to healthcare such as cost of appointments or delays in making appointments often lead to delays in the diagnosis of ASD. [16] In the UK the National Autism Plan for Children recommends at most 30 weeks from first concern to completed diagnosis and assessment, though few cases are handled that quickly in practice. [6] Lack of access to appropriate medical care, broadening diagnostic criteria and increased awareness surrounding ASD in recent years has resulted in an increased number of individuals receiving a diagnosis of ASD as adults. Diagnosis of ASD in adults poses unique challenges because it still relies on an accurate developmental history and because autistic adults sometimes learn coping strategies, known as "masking" or "camouflaging", which may make it more difficult to obtain a diagnosis. [17] [18]
The presentation and diagnosis of autism spectrum disorder may vary based on sex and gender identity. Most studies that have investigated the impact of gender on presentation and diagnosis of autism spectrum disorder have not differentiated between the impact of sex versus gender. [19] There is some evidence that autistic women and girls tend to show less repetitive behavior and may engage in more camouflaging than autistic males. [20] Camouflaging may include making oneself perform normative facial expressions and eye contact. [21] Differences in behavioral presentation and gender-stereotypes may make it more challenging to diagnose autism spectrum disorder in a timely manner in females. [19] [20] A notable percentage of autistic females may be misdiagnosed, diagnosed after a considerable delay, or not diagnosed at all. [20]
Considering the unique challenges in diagnosing ASD using behavioral and observational assessment, specific US practice parameters for its assessment were published by the American Academy of Neurology in the year 2000, [22] the American Academy of Child and Adolescent Psychiatry in 1999, [5] and a consensus panel with representation from various professional societies in 1999. [22] The practice parameters outlined by these societies include an initial screening of children by general practitioners (i.e., "Level 1 screening") and for children who fail the initial screening, a comprehensive diagnostic assessment by experienced clinicians (i.e. "Level 2 evaluation"). Furthermore, it has been suggested that assessments of children with suspected ASD be evaluated within a developmental framework, include multiple informants (e.g., parents and teachers) from diverse contexts (e.g., home and school), and employ a multidisciplinary team of professionals (e.g., clinical psychologists, neuropsychologists, and psychiatrists). [23]
As of 2019 [update] , psychologists wait until a child showed initial evidence of ASD tendencies, then administer various psychological assessment tools to assess for ASD. [23] Among these measurements, the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS) are considered the "gold standards" for assessing autistic children. [24] [25] The ADI-R is a semi-structured parent interview that probes for symptoms of autism by evaluating a child's current behavior and developmental history. The ADOS is a semi-structured interactive evaluation of ASD symptoms that is used to measure social and communication abilities by eliciting several opportunities for spontaneous behaviors (e.g., eye contact) in standardized context. Various other questionnaires (e.g., The Childhood Autism Rating Scale, Autism Treatment Evaluation Checklist) and tests of cognitive functioning (e.g., The Peabody Picture Vocabulary Test) are typically included in an ASD assessment battery. The diagnostic interview for social and communication disorders (DISCO) may also be used. [26]
About half of parents of children with ASD notice their child's atypical behaviors by age 18 months, and about four-fifths notice by age 24 months. [14] If a child does not meet any of the following milestones, it "is an absolute indication to proceed with further evaluations. Delay in referral for such testing may delay early diagnosis and treatment and affect the [child's] long-term outcome." [22]
The Japanese practice is to screen all children for ASD at 18 and 24 months, using autism-specific formal screening tests. In contrast, in the UK, children whose families or doctors recognize possible signs of autism are screened. It is not known which approach is more effective. [28] [ clarification needed ] The UK National Screening Committee does not recommend universal ASD screening in young children. Their main concerns includes higher chances of misdiagnosis at younger ages and lack of evidence of effectiveness of early interventions. [29] There is no consensus between professional and expert bodies in the US on screening for autism in children younger than 3 years. [31]
Screening tools include the Modified Checklist for Autism in Toddlers (M-CHAT), the Early Screening of Autistic Traits Questionnaire, and the First Year Inventory; initial data on M-CHAT and its predecessor, the Checklist for Autism in Toddlers (CHAT), on children aged 18–30 months suggests that it is best used in a clinical setting and that it has low sensitivity (many false-negatives) but good specificity (few false-positives). [14] It may be more accurate to precede these tests with a broadband screener that does not distinguish ASD from other developmental disorders. [32] Screening tools designed for one culture's norms for behaviors like eye contact may be inappropriate for a different culture. [33] Although genetic screening for autism is generally still impractical, it can be considered in some cases, such as children with neurological symptoms and dysmorphic features. [34]
There is a significant level of misdiagnosis of autism in neurodevelopmentally typical children; 18–37% of children diagnosed with ASD eventually lose their diagnosis. This high rate of lost diagnosis cannot be accounted for by successful ASD treatment alone. The most common reason parents reported as the cause of lost ASD diagnosis was new information about the child (73.5%), such as a replacement diagnosis. Other reasons included a diagnosis given so the child could receive ASD treatment (24.2%), ASD treatment success or maturation (21%), and parents disagreeing with the initial diagnosis (1.9%). [30] [ non-primary source needed ]
Many of the children who were later found not to meet ASD diagnosis criteria then received diagnosis for another developmental disorder. Most common was ADHD, but other diagnoses included sensory disorders, anxiety, personality disorder, or learning disability. [30] [ non-primary source needed ] Neurodevelopment and psychiatric disorders that are commonly misdiagnosed as ASD include specific language impairment, social communication disorder, anxiety disorder, reactive attachment disorder, cognitive impairment, visual impairment, hearing loss and normal behavioral variation. [35] Some behavioral variations that resemble autistic traits are repetitive behaviors, sensitivity to change in daily routines, focused interests, and toe-walking. These are considered normal behavioral variations when they do not cause impaired function. Boys are more likely to exhibit repetitive behaviors especially when excited, tired, bored, or stressed. Some ways of distinguishing typical behavioral variations from autistic behaviors are the ability of the child to suppress these behaviors and the absence of these behaviors during sleep. [10]
Asperger syndrome (AS), also known as Asperger's syndrome or Asperger's, is a term formerly used to describe a neurodevelopmental condition characterized by significant difficulties in social interaction and nonverbal communication, along with restricted, repetitive patterns of behavior and interests. Asperger syndrome has been merged with other conditions into autism spectrum disorder (ASD) and is no longer considered a stand-alone diagnosis. It was considered milder than other diagnoses which were merged into ASD due to relatively unimpaired spoken language and intelligence.
The diagnostic category pervasive developmental disorders (PDD), as opposed to specific developmental disorders (SDD), was a group of disorders characterized by delays in the development of multiple basic functions including socialization and communication. It was defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM), and the International Classification of Diseases (ICD).
Developmental disorders comprise a group of psychiatric conditions originating in childhood that involve serious impairment in different areas. There are several ways of using this term. The most narrow concept is used in the category "Specific Disorders of Psychological Development" in the ICD-10. These disorders comprise developmental language disorder, learning disorders, developmental coordination disorders, and autism spectrum disorders (ASD). In broader definitions, attention deficit hyperactivity disorder (ADHD) is included, and the term used is neurodevelopmental disorders. Yet others include antisocial behavior and schizophrenia that begins in childhood and continues through life. However, these two latter conditions are not as stable as the other developmental disorders, and there is not the same evidence of a shared genetic liability.
Pervasive developmental disorder not otherwise specified (PDD-NOS) is a historic psychiatric diagnosis first defined in 1980 that has since been incorporated into autism spectrum disorder in the DSM-5 (2013).
Autism spectrum disorder (ASD) is a neurodevelopmental disorder that begins in early childhood, persists throughout adulthood, and affects two crucial areas of development: social communication and restricted, repetitive patterns of behavior. There are many conditions comorbid to autism spectrum disorder such as attention-deficit hyperactivity disorder and epilepsy.
Nonverbal learning disorder is a proposed category of neurodevelopmental disorder characterized by core deficits in visual-spatial processing and a significant discrepancy between verbal and nonverbal intelligence. A review of papers found that proposed diagnostic criteria were inconsistent. Proposed additional diagnostic criteria include intact verbal intelligence, and deficits in the following: visuoconstruction abilities, speech prosody, fine motor coordination, mathematical reasoning, visuospatial memory and social skills. NVLD is not recognised by the DSM-5 and is not clinically distinct from learning disorders.
The Autism Diagnostic Observation Schedule (ADOS) is a standardized diagnostic test for assessing autism spectrum disorder. The protocol consists of a series of structured and semi-structured tasks that involve social interaction between the examiner and the person under assessment. The examiner observes and identifies aspects of the subject's behavior, assigns these to predetermined categories, and combines these categorized observations to produce quantitative scores for analysis. Research-determined cut-offs identify the potential diagnosis of autism spectrum disorder, allowing a standardized assessment of autistic symptoms.
Autism therapies include a wide variety of therapies that help people with autism, or their families. Such methods of therapy seek to aid autistic people in dealing with difficulties and increase their functional independence.
The epidemiology of autism is the study of the incidence and distribution of autism spectrum disorders (ASD). A 2022 systematic review of global prevalence of autism spectrum disorders found a median prevalence of 1% in children in studies published from 2012 to 2021, with a trend of increasing prevalence over time. However, the study's 1% figure may reflect an underestimate of prevalence in low- and middle-income countries.
Pathological demand avoidance (PDA) or extreme demand avoidance (EDA) is a proposed disorder, and proposed sub-type of autism spectrum disorder, defined by characteristics such as a demand avoidance—which is a greater-than-typical refusal to comply with requests or expectations—and extreme efforts to avoid social demands. Any expectation, even routine activities, such as brushing teeth, or highly desired activities, such as getting ready to leave home to visit a playground, can trigger avoidant behavior. If the demand cannot be avoided, a panic attack or a meltdown may ensue.
Classic autism, also known as childhood autism, autistic disorder, (early) infantile autism, infantile psychosis, Kanner's autism, Kanner's syndrome, or (formerly) just autism, is a neurodevelopmental condition first described by Leo Kanner in 1943. It is characterized by atypical and impaired development in social interaction and communication as well as restricted, repetitive behaviors, activities, and interests. These symptoms first appear in early childhood and persist throughout life.
Autism, also called autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental disorder characterized by symptoms of deficient reciprocal social communication and the presence of restricted, repetitive, and inflexible patterns of behavior that are impairing in multiple contexts, excessive or atypical, or developmentally and socioculturally inappropriate. Other common signs include difficulty with social interaction, verbal and nonverbal communication, along with perseverative interests, stereotypic body movements, rigid routines, and hyper- or hyporeactivity to sensory input. Autism is clinically regarded as a spectrum disorder, meaning that it can manifest very differently in each person. For example, some are nonspeaking, while others have proficient spoken language. Because of this, there is wide variation in the support needs of people across the autism spectrum.
Childhood schizophrenia is similar in characteristics of schizophrenia that develops at a later age, but has an onset before the age of 13 years, and is more difficult to diagnose. Schizophrenia is characterized by positive symptoms that can include hallucinations, delusions, and disorganized speech; negative symptoms, such as blunted affect and avolition and apathy, and a number of cognitive impairments. Differential diagnosis is problematic since several other neurodevelopmental disorders, including autism spectrum disorder, language disorder, and attention deficit hyperactivity disorder, also have signs and symptoms similar to childhood-onset schizophrenia.
Autism spectrum disorder (ASD) refers to a variety of conditions typically identified by challenges with social skills, communication, speech, and repetitive sensory-motor behaviors. The 11th International Classification of Diseases (ICD-11), released in January 2021, characterizes ASD by the associated deficits in the ability to initiate and sustain two-way social communication and restricted or repetitive behavior unusual for the individual's age or situation. Although linked with early childhood, the symptoms can appear later as well. Symptoms can be detected before the age of two and experienced practitioners can give a reliable diagnosis by that age. However, official diagnosis may not occur until much older, even well into adulthood. There is a large degree of variation in how much support a person with ASD needs in day-to-day life. This can be classified by a further diagnosis of ASD level 1, level 2, or level 3. Of these, ASD level 3 describes people requiring very substantial support and who experience more severe symptoms. ASD-related deficits in nonverbal and verbal social skills can result in impediments in personal, family, social, educational, and occupational situations. This disorder tends to have a strong correlation with genetics along with other factors. More research is identifying ways in which epigenetics is linked to autism. Epigenetics generally refers to the ways in which chromatin structure is altered to affect gene expression. Mechanisms such as cytosine regulation and post-translational modifications of histones. Of the 215 genes contributing, to some extent in ASD, 42 have been found to be involved in epigenetic modification of gene expression. Some examples of ASD signs are specific or repeated behaviors, enhanced sensitivity to materials, being upset by changes in routine, appearing to show reduced interest in others, avoiding eye contact and limitations in social situations, as well as verbal communication. When social interaction becomes more important, some whose condition might have been overlooked suffer social and other exclusion and are more likely to have coexisting mental and physical conditions. Long-term problems include difficulties in daily living such as managing schedules, hypersensitivities, initiating and sustaining relationships, and maintaining jobs.
Diagnosis, treatment, and experiences of autism varies globally. Although the diagnosis of autism is rising in post-industrial nations, diagnosis rates are much lower in developing nations.
The Autism Treatment Evaluation Scale (ATEC) is a 77-item diagnostic assessment tool that was developed by Bernard Rimland and Stephen Edelson at the Autism Research Institute. The ATEC was originally designed to evaluate the effectiveness of autism treatments, but it may also be beneficial as a screening tool for children. The questionnaire, which is completed by a parent, takes about 10–15 minutes to complete and is designed for use with children ages 5–12. The ATEC is currently available in 17 different languages.
The Modified Checklist for Autism in Toddlers (M-CHAT) is a psychological questionnaire that evaluates risk for autism spectrum disorder in children ages 16–30 months. The 20-question test is filled out by the parent, and a follow-up portion is available for children who are classified as medium- to high-risk for autism spectrum disorder. Children who score in the medium to high-risk zone may not necessarily meet criteria for a diagnosis. The checklist is designed so that primary care physicians can interpret it immediately and easily. The M-CHAT has shown fairly good reliability and validity in assessing child autism symptoms in recent studies.
Sex and gender differences in autism exist regarding prevalence, presentation, and diagnosis.
The Ritvo Autism & Asperger Diagnostic Scale (RAADS) is a psychological self-rating scale developed by Dr. Riva Ariella Ritvo. An abridged and translated 14 question version was then developed at the Department of Clinical Neuroscience at the Karolinska Institute, to aid in the identification of patients who may have undiagnosed ASD.
Social (pragmatic) communication disorder (SPCD), also known as pragmatic language impairment (PLI), is a neurodevelopmental disorder characterized by difficulties in the social use of verbal and nonverbal communication. Individuals who are defined by the acronym "SPCD" struggle to effectively indulge in social interactions, interpret social cues, and may struggle to use words appropriately in social contexts.
Some individuals with Autism Spectrum Disorder are capable of functioning adequately by making an exceptional effort to compensate for their symptoms during childhood, adolescence or adulthood. Such sustained effort, which may be more typical of affected females, can have a deleterious impact on mental health and well-being.