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84-454: Autism , or autism spectrum disorder ( ASD ), is a neurodevelopmental disorder characterized by repetitive, restricted, and inflexible patterns of behavior, interests, and activities, as well as difficulties in social interaction and social communication. Autism generally affects a person's ability to understand and connect with others, as well as their adaptability to everyday situations, with its severity and support needs varying widely across

168-445: A neurodevelopmental disorder , but the autism rights movement (and some researchers) see autistic people as part of humanity's natural neurodiversity . From this point of view, autistic people may also be diagnosed with a disability of some sort, but that disability may be rooted in the systemic structures of a society rather than in the person; thus, proponents argue that autistic people should be accommodated rather than cured. On

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336-603: A "level" system, which ranks how in need of support the patient is, level 1 being the mildest and level 3 the severest, while the ICD-11 system has two axes, intellectual impairment and language impairment, as these are seen as the most crucial factors. Autism is currently defined as a highly variable neurodevelopmental disorder that is generally thought to cover a broad and deep spectrum , manifesting very differently from one person to another. Some have high support needs, may be nonspeaking , and experience developmental delays; this

420-438: A broader medical condition or syndrome , representing about 25% of ASD cases. The causes of syndromic autism are often known, and monogenic disorders account for approximately 5% of these cases. Non-syndromic autism, also known as classic or idiopathic autism, represents the majority of cases, and its cause is typically polygenic and unknown. Autism has a strong genetic basis, although the genetics of autism are complex and it

504-534: A dimension of symptom severity, subjective distress, and functional impairment. A consequence of this dimensionality is substantial variability in the nature and extent of support a person with ASD requires. A formal diagnosis of ASD requires not merely the presence of ASD symptoms, but symptoms that cause significant impairment in multiple domains of functioning, in addition to being excessive or atypical enough to be developmentally and socioculturally inappropriate. Attention deficit hyperactivity disorder (ADHD)

588-489: A diminished quality of life and a direct average reduction in life expectancy of 13 years. ADHD is associated with other neurodevelopmental and mental disorders as well as non-psychiatric disorders, which can cause additional impairment. Motor disorders including developmental coordination disorder , stereotypic movement disorder , and tic disorders (such as Tourette's syndrome ), and apraxia of speech . Deficits in any area of information processing can manifest in

672-643: A low demand for coordination that ameliorated many challenges associated with disruptive turns." Autistic interests, and thus conversational topics, seem to be largely driven by an intense interest in specific topics ( monotropism ). Historically, autistic children were said to be delayed in developing a theory of mind , and the empathizing–systemizing theory has argued that while autistic people have compassion ( affective empathy ) for others with similar presentation of symptoms, they have limited, though not necessarily absent, cognitive empathy . This may present as social naïvety, lower than average intuitive perception of

756-572: A model of social patterns, and develop coping mechanisms, referred to as " masking ", which have recently been found to come with psychological costs and a higher increased risk of suicidality. ASD includes a wide variety of characteristics. Some of these include behavioral characteristics which widely range from slow development of social and learning skills to difficulties creating connections with other people. Autistic people may experience these challenges with forming connections due to anxiety or depression, which they are more likely to experience, and as

840-495: A more specific neurodevelopmental manifestation. Some deficits may be predicted from observed deviations in the maturation patterns of the infant gut microbiome . Deprivation from social and emotional care causes severe delays in brain and cognitive development. Studies with children growing up in Romanian orphanages during Nicolae Ceauşescu 's regime reveal profound effects of social deprivation and language deprivation on

924-918: A neurotypical bias in autism research, which has come to be scrutinized for "dehumanization, objectification, and stigmatization". Recent research has proposed that autistics' lack of readability and a neurotypical lack of effort to interpret atypical signals may cause a negative interaction loop, increasingly driving both groups apart into two distinct groups with different social interaction styles. Differences in verbal communication begin to be noticeable in childhood, as many autistic children develop language skills at an uneven pace. Verbal communication may be delayed or never develop ( nonverbal autism ), while reading ability may be present before school age ( hyperlexia ). Reduced joint attention seem to distinguish autistic from non-autistic infants. Infants may show delayed onset of babbling , unusual gestures, diminished responsiveness, and vocal patterns that are not synchronized with

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1008-419: A parent, guardian, teacher, or other responsible adult has raised concerns to a doctor. Neurodevelopmental disorders may also be confirmed by genetic testing . Traditionally, disease related genetic and genomic factors are detected by karyotype analysis , which detects clinically significant genetic abnormalities for 5% of children with a diagnosed disorder. As of 2017 , chromosomal microarray analysis (CMA)

1092-572: A person can depend on context, and may vary over time. While the DSM and ICD greatly influence each other, there are also differences. For example, Rett syndrome was included in ASD in the DSM-5, but in the ICD-11 it was excluded and placed in the chapter on Developmental Anomalies. The ICD and the DSM change over time, and there has been collaborative work toward a convergence of the two since 1980 (when DSM-III

1176-503: A person's ASD diagnosis did not influence their interest level. Thus, there has been a recent shift to acknowledge that autistic people may simply respond and behave differently than people without ASD. So far, research has identified two unconventional features by which autistic people create shared understanding ( intersubjectivity ): "a generous assumption of common ground that, when understood, led to rapid rapport, and, when not understood, resulted in potentially disruptive utterances; and

1260-547: A pervasive feature of the individual's functioning observable in all settings, although they may vary according to social, educational, or other context. Individuals along the spectrum exhibit a full range of intellectual functioning and language abilities. ICD-11 was produced by professionals from 55 countries out of the 90 involved and is the most widely used reference worldwide. The American Psychiatric Association 's Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision ( DSM-5-TR ), released in 2022,

1344-470: A primary neurodevelopmental disorder. For example HIV Infections of the head and brain, like brain abscesses , meningitis or encephalitis have a high risk of causing neurodevelopmental problems and eventually a disorder. For example, measles can progress to subacute sclerosing panencephalitis . A number of infectious diseases can be transmitted congenitally (either before or at birth), and can cause serious neurodevelopmental problems, as for example

1428-625: A result isolate themselves. Other behavioral characteristics include abnormal responses to sensations (such as sights, sounds, touch, taste and smell) and problems keeping a consistent speech rhythm. The latter problem influences social skills, leading to potential problems in understanding for interlocutors. Autistic people's behavioral characteristics typically influence development, language, and social competence. Their behavioral characteristics can be observed as perceptual disturbances, disturbances of development rate, relating, speech and language, and motility. The second core symptom of autism spectrum

1512-422: A set of closely related and overlapping diagnoses such as Asperger syndrome and the syndrome formerly known as Kanner syndrome . This created unclear boundaries between the terms, so for the DSM-5 and ICD-11, a spectrum approach was taken. The new system is also more restrictive, meaning fewer people qualify for diagnosis. The DSM-5 and ICD-11 use different categorization tools to define this spectrum. DSM-5 uses

1596-488: A small effect, and some of which are rare and have a large effect. The most common gene disrupted with large effect rare variants appeared to be CHD8 , but less than 0.5% of autistic people have such a mutation. The gene CHD8 encodes the protein chromodomain helicase DNA binding protein 8, which is a chromatin regulator enzyme that is essential during fetal development. CHD8 is an adenosine triphosphate (ATP)–dependent enzyme. The protein contains an Snf2 helicase domain that

1680-597: A steady course without remission (different developmental timelines are described in more detail below). Autistic people may be severely impaired in some respects but average, or even superior, in others. Clinicians consider assessment for ASD when a patient shows: These features are typically assessed with the following, when appropriate: There are many signs associated with autism; the presentation varies widely: The broader autism phenotype describes people who may not have ASD but do have autistic traits , such as abnormalities in eye contact and stimming . According to

1764-446: A substantial fraction of autism cases may be traceable to genetic causes that are highly heritable but not inherited: that is, the mutation that causes the autism is not present in the parental genome. As of 2018, understanding of genetic risk factors had shifted from a focus on a few alleles to an understanding that genetic involvement in ASD is probably diffuse, depending on a large number of variants, some of which are common and have

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1848-469: A tendency to be associated with sedation and weight gain . Melatonin supplementation has been shown to improve insomnia related to autism. Stimulant therapy may improve mental processing speed when there is comorbid ADHD. Before the DSM-5 (2013) and ICD-11 (2022) diagnostic manuals were adopted, ASD was found under the diagnostic category pervasive developmental disorder . The previous system relied on

1932-529: A trend of increasing prevalence over time. This increasing prevalence has reinforced the myth perpetuated by anti-vaccine activists that autism is caused by vaccines . Boys are also significantly far more frequently diagnosed than girls . There is no cure for autism. Some advocates of autistic people argue that efforts to find a cure are misguided and even harmful. Early intervention services based on applied behavior analysis (ABA) aim to teach children self-care, social and communicative skills. Guidelines from

2016-529: A variety of specific learning disabilities (SLD). It is possible for an individual to have more than one of these difficulties. This is referred to as comorbidity or co-occurrence of learning disabilities. In the UK, the term dual diagnosis is often used to refer to co-occurrence of learning difficulties. There are neurodevelopmental research projects examining potential new classifications of disorders including: The multitude of neurodevelopmental disorders span

2100-518: A wide range of associated symptoms and severity, resulting in different degrees of mental, emotional, physical, and economic consequences for individuals, and in turn families, social groups, and society. The development of the nervous system is tightly regulated and timed; it is influenced by both genetic programs and the prenatal environment. Any significant deviation from the normal developmental trajectory early in life can result in missing or abnormal neuronal architecture or connectivity. Because of

2184-493: Is accompanied by another . Intellectual disability , also known as general learning disability is a disorder that affects the ability to learn, retain, or process information; to think critically or abstractly, and to solve problems. Adaptive behaviour is limited, affecting daily living activities . Global developmental delay is categorized under intellectual disability and is diagnosed when several areas of intellectual functioning are affected. A communication disorder

2268-726: Is folic acid deficiency in the mother, a B vitamin usually found in fruits, vegetables, whole grains, and milk products. (Neural tube defects are also caused by medications and other environmental causes, many of which interfere with folate metabolism, thus they are considered to have multifactorial causes.) Another deficiency, iodine deficiency , produces a spectrum of neurodevelopmental disorders ranging from mild emotional disturbance to severe intellectual disability. (see also congenital iodine deficiency syndrome ). Excesses in both maternal and infant diets may cause disorders as well, with foods or food supplements proving toxic in large amounts. For instance in 1973 K.L. Jones and D.W. Smith of

2352-477: Is a common cause (over 400,000 injuries per year in the US alone, without clear information as to how many produce developmental sequellae) of neurodevelopmental syndromes. It may be subdivided into two major categories, congenital injury (including injury resulting from otherwise uncomplicated premature birth) and injury occurring in infancy or childhood. Common causes of congenital injury are asphyxia (obstruction of

2436-611: Is a neurodevelopmental disorder characterised by executive dysfunction occasioning symptoms of inattention , hyperactivity, impulsivity and emotional dysregulation that are excessive and pervasive, impairing in multiple contexts, and developmentally-inappropriate . ADHD symptoms arise from executive dysfunction, and emotional dysregulation is often considered a core symptom. Difficulties in self-regulation such as time management, inhibition and sustained attention may cause poor professional performance, relationship difficulties and numerous health risks, collectively predisposing to

2520-456: Is a neurodevelopmental disorder characterized by symptoms of deficient reciprocal social communication and the presence of restricted, repetitive, and inflexible patterns of behavior. While its severity and specific manifestations vary widely across the spectrum, autism generally affects a person's ability to understand and connect with others, as well as their adaptability to everyday situations. Like most developmental disorders, autism exists along

2604-721: Is a pattern of restricted and repetitive behaviors, activities, and interests. In order to be diagnosed with ASD under the DSM-5-TR, a person must have at least two of the following behaviors: Autistic people can display many forms of repetitive or restricted behavior, which the Repetitive Behavior Scale-Revised (RBS-R) categorizes as follows. Self-injurious behaviors are relatively common in autistic people, and can include head-banging, self-cutting, self-biting, and hair-pulling. Some of these can result in serious injury or death. Following are theories about

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2688-729: Is acquired during childhood. Autistic people display atypical nonverbal behaviors or show differences in nonverbal communication . They may make infrequent eye contact , even when called by name, or avoid it altogether. This may be due to the high amount of sensory input received when making eye contact. Autistic people often recognize fewer emotions and their meaning from others' facial expressions, and may not respond with facial expressions expected by their non-autistic peers. Temple Grandin , an autistic woman involved in autism activism, described her inability to understand neurotypicals ' social communication as leaving her feeling "like an anthropologist on Mars". Autistic people struggle to understand

2772-448: Is any disorder that affects an individual's ability to comprehend , detect, or apply language and speech to engage in dialogue effectively with others. This also encompasses deficiencies in verbal and nonverbal communication styles. Examples include stuttering , sound substitution , inability to understand or use one's native language. Autism , also called autism spectrum disorder (ASD) or autism spectrum condition (ASC),

2856-659: Is bidirectional, research on communication difficulties has since also begun to study non-autistic behavior, with researcher Catherine Crompton writing in 2020 that non-autistic people "struggle to identify autistic mental states, identify autistic facial expressions, overestimate autistic egocentricity, and are less willing to socially interact with autistic people. Thus, although non-autistic people are generally characterised as socially skilled, these skills may not be functional, or effectively applied, when interacting with autistic people." Any previously observed communication deficits of autistic people may thus have been constructed through

2940-585: Is heritable. After an older child is diagnosed with ASD, 7% to 20% of subsequent children are likely to be as well. If parents have one autistic child, they have a 2% to 8% chance of having a second child who is autistic. If the autistic child is an identical twin, the other will be affected 36% to 95% of the time. A fraternal twin is affected up to 31% of the time. The large number of autistic people with unaffected family members may result from spontaneous structural variation , such as deletions , duplications or inversions in genetic material during meiosis . Hence,

3024-418: Is lowered activity in the fusiform face area of the brain, which is associated with impaired perception of people versus objects. It has been proposed to classify autism using genetics as well as behavior. Autism spectrum disorder (ASD) can be classified into two categories: "syndromic autism" and "non-syndromic autism". Syndromic autism refers to cases where ASD is one of the characteristics associated with

3108-520: Is more likely with other co-existing diagnoses. Others have relatively low support needs; they may have more typical speech-language and intellectual skills but atypical social/conversation skills, narrowly focused interests , and wordy, pedantic communication. They may still require significant support in some areas of their lives. The spectrum model should not be understood as a continuum running from mild to severe, but instead means that autism can present very differently in each person. How it presents in

3192-706: Is possible to identify general factors, but much more difficult to pinpoint specific ones. Given the current state of knowledge, prediction can only be of a global nature and so requires the use of general markers. Research into causes has been hampered by the inability to identify biologically meaningful subgroups within the autistic population and by the traditional boundaries between the disciplines of psychiatry , psychology , neurology and pediatrics . Newer technologies such as fMRI and diffusion tensor imaging can help identify biologically relevant phenotypes (observable traits) that can be viewed on brain scans , to help further neurogenetic studies of autism; one example

3276-475: Is related to other chromosomal abnormalities such as translocation of the genetic material. It is characterized by short stature , epicanthal ( eyelid ) folds, abnormal fingerprints , and palm prints , heart defects , poor muscle tone (delay of neurological development), and intellectual disabilities (delay of intellectual development). Less commonly known genetically determined neurodevelopmental disorders include Fragile X syndrome . Fragile X syndrome

3360-421: Is responsible for the hydrolysis of ATP to adenosine diphosphate (ADP). CHD8 encodes a DNA helicase that functions as a repressor of transcription, remodeling chromatin structure by altering the position of nucleosomes. CHD8 negatively regulates Wnt signaling . Wnt signaling is important in the vertebrate early development and morphogenesis. It is believed that CHD8 also recruits the linker histone H1 and causes

3444-598: Is that they negatively impact a person's functioning in one or more domains of life (personal, social, academic, occupational) depending on the disorder and deficits it has caused. All of these disorders and their levels of impairment exist on a spectrum, and affected individuals can experience varying degrees of symptoms and deficits, despite having the same diagnosis. The DSM-5 classifies neurodevelopmental disorders into six overarching groups: intellectual , communication , autism , attention deficit hyperactivity , motor , and specific learning disorders . Often one disorder

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3528-724: Is the current version of the DSM. It is the predominant mental health diagnostic system used in the United States and Canada, and is often used in Anglophone countries. Its fifth edition, DSM-5 , released in May 2013, was the first to define ASD as a single diagnosis, which is still the case in the DSM-5-TR. ASD encompasses previous diagnoses, including the four traditional diagnoses of autism— classic autism , Asperger syndrome , childhood disintegrative disorder , and pervasive developmental disorder not otherwise specified (PDD-NOS)—and

3612-458: Is unclear whether ASD is explained more by rare mutations with major effects, or by rare multi-gene interactions of common genetic variants. Complexity arises due to interactions among multiple genes, the environment, and epigenetic factors which do not change DNA sequencing but are heritable and influence gene expression . Many genes have been associated with autism through sequencing the genomes of affected people and their parents. But most of

3696-787: The Centres for Disease Control (CDC), NICE and European Society for Child & Adolescent Psychiatry (ESCAP) endorse the use of ABA as it reduces symptoms that impair daily functioning and quality of life, although NICE acknowledges that ABA does not meet the highest level of evidence-quality. Additionally, some in the autism rights movement oppose its application due to a perception that it emphasises normalisation. Speech and occupational therapy , as well as augmentative and alternative modes of communication , are effective adjunctive therapies . At present, no medication has been shown to reduce "core symptoms" of ASD. However, some atypical antipsychotics can alleviate comorbid irritability, though with

3780-488: The Review Journal of Autism and Developmental Disorders published a systematic review of 21 studies investigating associations between ASD, problematic internet use, and gaming disorder where the majority of the studies found positive associations between the disorders. Exactly what causes autism remains unknown. It was long mostly presumed that there is a common cause at the genetic, cognitive, and neural levels for

3864-527: The University of Washington Medical School in Seattle found a pattern of "craniofacial, limb, and cardiovascular defects associated with prenatal onset growth deficiency and developmental delay" in children of alcoholic mothers, now called fetal alcohol syndrome , It has significant symptom overlap with several other entirely unrelated neurodevelopmental disorders. Brain trauma in the developing human

3948-696: The imprinted brain hypothesis and the extreme male brain theory . Neurodevelopmental disorder Neurodevelopmental disorders are a group of mental conditions affecting the development of the nervous system , which includes the brain and spinal cord . According to the American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, ( DSM-5 ) published in 2013, these conditions generally appear in early childhood, usually before children start school, and can persist into adulthood. The key characteristic of all these disorders

4032-421: The trachea ), hypoxia (lack of oxygen to the brain), and the mechanical trauma of the birth process itself. Although it not clear yet as strong is the correlation between placenta and brain, a growing number of studies are linking placenta to fetal brain development. Neurodevelopmental disorders are diagnosed by evaluating the presence of characteristic symptoms or behaviors in a child, typically after

4116-881: The underlying spectrum . For example, some are nonverbal , while others have proficient spoken language. A formal diagnosis of ASD according to either the DSM-5 or the ICD-11 criteria requires not merely the presence of ASD symptoms, but symptoms that cause significant impairment in multiple domains of functioning, in addition to being atypical or excessive for the individual's age and sociocultural context. Common signs of ASD include difficulty with social interaction and verbal and nonverbal communication , along with perseverative interests , stereotypic body movements , rigid routines, and hyper- or hypo-reactivity to sensory input . The World Health Organization (WHO), UK National Institute for Health and Care Excellence (NICE), and American Psychological Association classify autism as

4200-449: The DSM-5, the DSM separated social deficits and communication deficits into two domains. Further, the DSM-5 changed to an onset age in the early developmental period, with a note that symptoms may manifest later when social demands exceed capabilities, rather than the previous, more restricted three years of age. These changes remain in the DSM-5-TR. For many autistic people, characteristics first appear during infancy or childhood and follow

4284-514: The caregiver. In the second and third years, autistic children may 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 more likely to simply repeat others' words ( echolalia ). The CDC estimated in 2015 that around 40% of autistic children do not speak at all. Autistic adults' verbal communication skills largely depend on when and how well speech

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4368-411: The cause of self-injurious behavior in children with developmental delay, including autistic children: The suicide rate for verbal autistics is nine times that of the general population. Studies have supported the common belief that autistic people become exhausted or burnt out in some situations. Autistic people may have symptoms that do not contribute to the official diagnosis, but that can affect

4452-545: The child during gestation . (See also teratology ). In a child, type 1 diabetes can produce neurodevelopmental damage by the effects of excess or insufficient glucose . The problems continue and may worsen throughout childhood if the diabetes is not well controlled. Type 2 diabetes may be preceded in its onset by impaired cognitive functioning. A non-diabetic fetus can also be subjected to glucose effects if its mother has undetected gestational diabetes . Maternal diabetes causes excessive birth size, making it harder for

4536-458: The contrary, other scientists argue that ASD impairs functioning in many ways that are inherent to the disorder itself and unrelated to society. The neurodiversity perspective has led to significant controversy among those who are autistic and advocates, practitioners, and charities. The precises causes of autism are unknown in most individual cases. Research shows that the disorder is highly heritable and polygenic, and neurobiological risks from

4620-508: The current disorder-focused spectrum model deconstruct autism into at least two separate phenomena: (1) a non-pathological spectrum of behavioral traits in the population, and (2) the neuropathological burden of rare genetic mutations and environmental risk factors potentially leading to neurodevelopmental and psychological disorders, (3) governed by an individual's cognitive ability to compensate. The World Health Organization 's International Classification of Diseases (11th Revision), ICD-11 ,

4704-471: The developing brain. These effects are time-dependent. The longer children stayed in negligent institutional care, the greater the consequences. By contrast, adoption at an early age mitigated some of the effects of earlier institutionalization . A prominent example of a genetically determined neurodevelopmental disorder is trisomy 21, also known as Down syndrome . This disorder usually results from an extra chromosome 21 , although in uncommon instances it

4788-780: The developing child, may produce neurodevelopmental disorders. One typical immune reaction in infants and children is PANDAS , or Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infection . Another disorder is Sydenham's chorea , which results in more abnormal movements of the body and fewer psychological sequellae. Both are immune reactions against brain tissue that follow infection by Streptococcus bacteria. Susceptibility to these immune diseases may be genetically determined, so sometimes several family members may have one or both of them following an epidemic of Strep infection. Systemic infections can result in neurodevelopmental consequences, when they occur in infancy and childhood of humans, but would not be called

4872-459: The development of the autism spectrum, but it cannot be guaranteed that they are determinants for the development. ASD may be under-diagnosed in women and girls due to an assumption that it is primarily a male condition, but genetic phenomena such as imprinting and X linkage have the ability to raise the frequency and severity of conditions in males, and theories have been put forward for a genetic reason why males are diagnosed more often, such as

4956-442: The environment are also relevant. Autism frequently co-occurs with attention deficit hyperactivity disorder (ADHD), epilepsy and intellectual disability , and research indicates that autistic people have significantly higher rates of LGBTQ+ identities and feelings than the general population. Disagreements persist about what should be included as part of the diagnosis, whether there are meaningful subtypes or stages of autism, and

5040-691: The exposure starts at a younger age. In April 2021, Research in Autism Spectrum Disorders published a systematic review of 12 studies of video game addiction in ASD subjects that found that children, adolescents, and adults with ASD are at greater risk of video game addiction than those without ASD, and that the data from the studies suggested that internal and external factors (sex, attention and oppositional behavior problems, social aspects, access and time spent playing video games, parental rules, and game genre) were significant predictors of video game addiction in ASD subjects. In March 2022,

5124-524: The fetus even if the fetus has not inherited the disease. This can produce intellectual disability and other disorders. Nutrition disorders and nutritional deficits may cause neurodevelopmental disorders, such as spina bifida , and the rarely occurring anencephaly , both of which are neural tube defects with malformation and dysfunction of the nervous system and its supporting structures, leading to serious physical disability and emotional sequelae. The most common nutritional cause of neural tube defects

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5208-410: The individual's age and sociocultural context. The onset of the disorder occurs during the developmental period, typically in early childhood, but symptoms may not become fully manifest until later, when social demands exceed limited capacities. Deficits are sufficiently severe to cause impairment in personal, family, social, educational, occupational or other important areas of functioning and are usually

5292-458: The infant to pass through the birth canal without injury or it can directly produce early neurodevelopmental deficits. Usually the neurodevelopmental symptoms will decrease in later childhood. Phenylketonuria , also known as PKU, can induce neurodevelopmental problems and children with PKU require a strict diet to prevent intellectual disability and other disorders. In the maternal form of PKU , excessive maternal phenylalanine can be absorbed by

5376-811: The interpersonal relationship difficulties between autistic people and their non-autistic counterparts and how to solve them through teaching neurotypical social skills, but newer research has also evaluated what autistic people want from friendships, such as a sense of belonging and good mental health. Children with ASD are more frequently involved in bullying situations than their non-autistic peers, and predominantly experience bullying as victims rather than perpetrators or victim-perpetrators, especially after controlling for comorbid psychopathology. Prioritizing dependability and intimacy in friendships during adolescence, coupled with lowered friendship quantity and quality, often lead to increased loneliness in autistic people. As they progress through life, autistic people observe and form

5460-401: The majority are of unknown causes. Metabolic disorders in either the mother or the child can cause neurodevelopmental disorders. Two examples are diabetes mellitus (a multifactorial disorder ) and phenylketonuria (an inborn error of metabolism ). Many such inherited diseases may directly affect the child's metabolism and neural development but less commonly they can indirectly affect

5544-1186: The medical model, autistic people experience social communications impairments . Until 2013, deficits in social function and communication were considered two separate symptom domains. The current social communication domain criteria for autism diagnosis require people to have deficits across three social skills: social-emotional reciprocity, nonverbal communication, and developing and sustaining relationships. A deficit-based view predicts that autistic–autistic interaction would be less effective than autistic–non-autistic interactions or even non-functional. But recent research has found that autistic–autistic interactions are as effective in information transfer as interactions between non-autistics are, and that communication breaks down only between autistics and non-autistics. Also contrary to social cognitive deficit interpretations, recent (2019) research recorded similar social cognitive performances in autistic and non-autistic adults, with both of them rating autistic individuals less favorably than non-autistic individuals; however, autistic individuals showed more interest in engaging with autistic people than non-autistic people did, and learning of

5628-495: The mutations that increase autism risk have not been identified. Typically, autism cannot be traced to a Mendelian (single-gene) mutation or to a single chromosome abnormality , and none of the genetic syndromes associated with ASD have been shown to selectively cause ASD. Numerous genes have been found, with only small effects attributable to any particular gene. Most loci individually explain less than 1% of cases of autism. As of 2018, it appeared that between 74% and 93% of ASD risk

5712-442: The other hand, genes controlling expression of glial and immune cells in the brain, e.g. astrocytes and microglia , respectively, are over-expressed, which correlates with increased number of glial and immune cells found in postmortem ASD brains. Some genes under investigation in ASD pathophysiology are those that affect the mTOR signaling pathway, which supports cell growth and survival. All these genetic variants contribute to

5796-575: The person or the family. In September 2018, the Review Journal of Autism and Developmental Disorders published a systematic review of 47 studies published from 2005 to 2016 that concluded that associations between autism spectrum disorder (ASD) and screen time was inconclusive. In May 2019, the Journal of Developmental and Behavioral Pediatrics published a systematic review of 16 studies that found that children and adolescents with ASD are exposed to more screen time than typically developing peers and that

5880-436: The presence of other disorders or factors that likely contribute to the symptoms, other neurodevelopmental or mental disorders, intellectual disability, or language impairment). The symptom domains are (a) social communication and (b) restricted, repetitive behaviors, and there is the option of specifying a separate severity—the negative effect of the symptoms on the person—for each domain, rather than just overall severity. Before

5964-418: The range of diagnoses that included the word "autism". Rather than distinguishing among these diagnoses, the DSM-5 and DSM-5-TR adopt a dimensional approach with one diagnostic category for disorders that fall under the autism spectrum umbrella. Within that category, the DSM-5 and the DSM include a framework that differentiates each person by dimensions of symptom severity, as well as by associated features (i.e.,

6048-910: The regulation of long non-coding RNAs (lncRNAs), and the regulation of X chromosome inactivation (XCI) initiation, via regulation of Xist long non-coding RNA, the master regulator of XCI, though competitive binding to Xist regulatory regions. Some ASD is associated with clearly genetic conditions, like fragile X syndrome , but only around 2% of autistic people have fragile X. Hypotheses from evolutionary psychiatry suggest that these genes persist because they are linked to human inventiveness, intelligence or systemising. Current research suggests that genes that increase susceptibility to ASD are ones that control protein synthesis in neuronal cells in response to cell needs, activity and adhesion of neuronal cells, synapse formation and remodeling, and excitatory to inhibitory neurotransmitter balance. Therefore, although up to 1,000 different genes are thought to increase

6132-767: The repression of β-catenin and p53 target genes. The importance of CHD8 can be observed in studies where CHD8-knockout mice died after 5.5 embryonic days because of widespread p53-induced apoptosis. Some studies have determined the role of CHD8 in autism spectrum disorder (ASD). CHD8 expression significantly increases during human mid-fetal development. The chromatin remodeling activity and its interaction with transcriptional regulators have shown to play an important role in ASD aetiology . The developing mammalian brain has conserved CHD8 target regions that are associated with ASD risk genes. The knockdown of CHD8 in human neural stem cells results in dysregulation of ASD risk genes that are targeted by CHD8. Recently CHD8 has been associated with

6216-452: The risk of ASD, all of them eventually affect normal neural development and connectivity between different functional areas of the brain in a similar manner that is characteristic of an ASD brain. Some of these genes are known to modulate production of the GABA neurotransmitter, the nervous system's main inhibitory neurotransmitter. These GABA-related genes are under-expressed in an ASD brain. On

6300-405: The significance of autism-associated traits in the wider population. The combination of broader criteria, increased awareness, and the potential increase of actual prevalence, has led to considerably increased estimates of autism prevalence since the 1990s. The WHO estimates about 1 in 100 children had autism between 2012 and 2021, as that was the average estimate in studies during that period, with

6384-542: The social and non-social components of ASD's symptoms, described as a triad in the classic autism criteria. But it is increasingly suspected that autism is instead a complex disorder whose core aspects have distinct causes that often cooccur. It is unlikely that ASD has a single cause; many risk factors identified in the research literature may contribute to ASD. These include genetics, prenatal and perinatal factors (meaning factors during pregnancy or very early infancy), neuroanatomical abnormalities, and environmental factors. It

6468-518: The social context and subtext of neurotypical conversational or printed situations, and form different conclusions about the content. Autistic people may not control the volume of their voice in different social settings. At least half of autistic children have atypical prosody . What may look like self-involvement or indifference to non-autistic people stems from autistic differences in recognizing how other people have their own personalities, perspectives, and interests. Most published research focuses on

6552-600: The temporal and spatial complexity of the developmental trajectory, there are many potential causes of neurodevelopmental disorders that may affect different areas of the nervous system at different times and ages. These range from social deprivation, genetic and metabolic diseases , immune disorders , infectious diseases , nutritional factors, physical trauma , and toxic and prenatal environmental factors. Some neurodevelopmental disorders, such as autism and other pervasive developmental disorders , are considered multifactorial syndromes which have many causes that converge to

6636-474: The utility or meaning of body language , social reciprocity, or social expectations, including the habitus , social cues , and some aspects of sarcasm, which to some degree may also be due to comorbid alexithymia . But recent research has increasingly questioned these findings, as the " double empathy problem " theory (2012) argues that there is a lack of mutual understanding and empathy between both non-autistic persons and autistic individuals. As communication

6720-472: The viruses HSV , CMV , rubella ( congenital rubella syndrome ), Zika virus , or bacteria like Treponema pallidum in congenital syphilis , which may progress to neurosyphilis if it remains untreated. Protozoa like Plasmodium or Toxoplasma which can cause congenital toxoplasmosis with multiple cysts in the brain and other organs, leading to a variety of neurological deficits. Some cases of schizophrenia may be related to congenital infections, though

6804-528: Was first described in 1943 by Martin and Bell, studying persons with family history of sex-linked "mental defects". Rett syndrome , another X-linked disorder, produces severe functional limitations. Williams syndrome is caused by small deletions of genetic material from chromosome 7 . The most common recurrent copy number variation disorder is DiGeorge syndrome (22q11.2 deletion syndrome), followed by Prader-Willi syndrome and Angelman syndrome . Immune reactions during pregnancy , both maternal and of

6888-476: Was proposed to replace karyotyping because of its ability to detect smaller chromosome abnormalities and copy-number variants , leading to greater diagnostic yield in about 20% of cases. The American College of Medical Genetics and Genomics and the American Academy of Pediatrics recommend CMA as standard of care in the US. European Child %26 Adolescent Psychiatry This article about

6972-569: Was published and ICD-9 was current), including more rigorous biological assessment—in place of historical experience—and a simplification of the classification system. As of 2023, empirical and theoretical research is leading to a growing consensus among researchers that the established ASD criteria are ineffective descriptors of autism as a whole, and that alternative research approaches must be encouraged, such as going back to autism prototypes, exploring new causal models of autism, or developing transdiagnostic endophenotypes . Proposed alternatives to

7056-463: Was released in June 2018 and came into full effect as of January 2022. It describes ASD as follows: Autism spectrum disorder is characterised by persistent deficits in the ability to initiate and to sustain reciprocal social interaction and social communication, and by a range of restricted, repetitive, and inflexible patterns of behaviour, interests or activities that are clearly atypical or excessive for

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