Asperger syndrome

Asperger syndrome (AS), also known as Asperger's syndrome or Asperger's, was a diagnostic label that was historically used to describe a neurodevelopmental disorder characterized by significant difficulties in social interaction and nonverbal communication, along with restricted and repetitive patterns of behavior and interests. The term was retired as a formal diagnosis when it was merged into autism spectrum disorder (ASD) in the WHO's ICD-11 and the APA's DSM-5-TR. These organizations no longer recognize Asperger syndrome as a distinct clinical diagnosis. AS was considered milder than other diagnoses. This change reflected a shift toward a unified understanding of autism-related conditions rather than a judgment about individuals previously diagnosed with AS. Despite its removal from contemporary medical classification systems, many people continued to identify with the term Asperger's because of its long-standing use, personal relevance, and the way it shaped their diagnostic history and community identity. The syndrome was named in 1976 by English psychiatrist Lorna Wing after the Austrian pediatrician Hans Asperger, who in 1944 described children in his care who struggled to form friendships, did not understand others' gestures or feelings, engaged in one-sided conversations about their favorite interests, and were clumsy. In 1990 (coming into effect in 1993), the diagnosis of Asperger syndrome was included in the tenth edition (ICD-10) of the World Health Organization's International Classification of Diseases, and in 1994 it was also included in the fourth edition (DSM-4) of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders. With the publication of DSM-5 in 2013, the syndrome was removed, and the symptoms are now included within autism spectrum disorder along with classic autism and pervasive developmental disorder not otherwise specified (PDD-NOS). It was similarly merged into autism spectrum disorder in the International Classification of Diseases (ICD-11) in 2018 (published, coming into effect in 2022). The exact cause of autism, including what was formerly known as Asperger syndrome, is not well understood. While it has high heritability, the underlying genetics have not been determined conclusively. Environmental factors are also believed to play a role. Brain imaging has not identified a common underlying condition. There is no single treatment, and the UK's National Health Service (NHS) guidelines suggest that "treatment" of any form of autism should not be a goal, since autism is not "a disease that can be removed or cured". According to the Royal College of Psychiatrists, while co-occurring conditions might require treatment, "management of autism itself is chiefly about the provision of the education, training, and social support/care required to improve the person's ability to function in the everyday world". The effectiveness of particular interventions for autism is supported by only limited data. Interventions may include social skills training, cognitive behavioral therapy, physical therapy, speech therapy, parent training, and medications for associated problems, such as mood or anxiety. Autistic characteristics tend to become less obvious in adulthood, but social and communication difficulties usually persist. In 2015, Asperger syndrome was estimated to affect 37.2 million people globally, or about 0.5% of the population. The exact percentage of people affected has still not been firmly established. Autism spectrum disorder is diagnosed in males more often than females, and females are typically diagnosed at a later age. The modern conception of Asperger syndrome came into existence in 1981 and went through a period of popularization. It became a standardized diagnosis in the 1990s, and was merged into ASD in 2013. Many questions and controversies about the condition remain.

== Classification == The extent of the overlap between Asperger syndrome and other forms of autism, particularly what was sometimes called high-functioning autism is unclear. The ASD classification is to some extent an artifact of how autism was discovered, and it may not reflect the true nature of the spectrum; methodological problems have beset Asperger syndrome as a valid diagnosis from the outset. As noted above, in the 2010s, Asperger syndrome, as a separate diagnosis, was eliminated and folded into autism spectrum disorder in the DSM-5 and the ICD-11. Like the diagnosis of Asperger syndrome, the change was controversial. The World Health Organization (WHO) previously defined Asperger syndrome (AS) as one of the pervasive developmental disorders (PDD), which are a spectrum of psychological disorders that are characterized by abnormalities of social interaction and communication that pervade the individual's functioning, and by restricted and repetitive interests and behavior. Like other neurodevelopmental conditions, ASD begins in infancy or childhood, has a steady course without remission or relapse, and has impairments that result from maturation-related changes in various systems of the brain.

== Characteristics ==

As a pervasive developmental disorder, Asperger syndrome is distinguished by a pattern of symptoms rather than a single symptom. It is characterized by qualitative impairment in social interaction, by stereotyped and restricted patterns of behavior, activities, and interests, and by no clinically significant delay in cognitive development or general delay in language. Intense preoccupation with a narrow subject, one-sided verbosity, restricted prosody, and physical clumsiness are typical of the condition, but are not required for diagnosis. Suicidal thoughts and behaviors are a serious concern within the autistic population. One study found that adults with Asperger syndrome exhibited suicidal thoughts at 9 times the rate of the general population. Of autistic study participants, 66% had experienced suicidal ideation, while 35% had planned or attempted suicide.

=== Social interaction ===

A lack of demonstrated empathy affects aspects of social relatability for persons with Asperger syndrome. Individuals with Asperger syndrome experience difficulties in basic elements of social interaction, which may include a failure to develop friendships or to seek shared enjoyments or achievements with others (e.g., showing others objects of interest); a lack of social or emotional reciprocity; and impaired nonverbal behaviors in areas such as eye contact, facial expression, posture, and gesture. People with Asperger syndrome may not be as withdrawn around others, compared with those with other forms of autism; they approach others, even if awkwardly. For example, a person with Asperger syndrome may engage in a one-sided, long-winded speech about a favorite topic, while misunderstanding or not recognizing the listener's feelings or reactions, such as a wish to change the topic of talk or end the interaction. This social awkwardness has been called "active but odd". Such failures to react appropriately to social interaction may appear as disregard for other people's feelings and may come across as rude or insensitive. However, not all individuals with Asperger syndrome will approach others. Some may even display selective mutism, not speaking at all to most people and excessively to specific others. The cognitive ability of children with Asperger syndrome often allows them to articulate social norms in a laboratory context, where they may be able to show a theoretical understanding of other people's emotions; however, they typically have difficulty acting on this knowledge in fluid, real-life situations. People with Asperger syndrome may analyze and distill their observations of social interaction into rigid behavioral guidelines and apply these rules in awkward ways, such as forced eye contact, resulting in a demeanor that appears rigid or socially naïve. A history of failed attempts to establish reciprocal social relationships can cause autistic individuals to isolate themselves and cease attempts to engage; however, autistic people overwhelmingly report a desire for social contact and friendship.

==== Violent or criminal behavior ==== The hypothesis that individuals with Asperger syndrome are predisposed to violent or criminal behavior has been investigated but is unsupported by data. More evidence suggests that children diagnosed with Asperger syndrome are more likely to be victims, rather than offenders. A 2008 review found that about 80% of reported violent criminals with Asperger syndrome also had other coexisting psychotic psychiatric disorders such as schizoaffective disorder. The sample size of this review was small (n = 37).

=== Empathy === People with an Asperger profile might not be recognized for their empathetic qualities, due to variation in the ways empathy is felt and expressed. Some people feel deep empathy, but do not outwardly communicate these sentiments through facial expressions or language. Some people come to empathy through intellectual processes, using logic and reasoning to arrive at the feelings. People with Asperger profiles may be bullied or excluded by peers, and might as a result be guarded around people, which could appear as lack of empathy. People with Asperger profiles can still be caring individuals; indeed, it is particularly common for those with the profile to feel and exhibit deep concern for individual rights, human welfare, animal rights, environmental protection, and other global and humanitarian causes. Evidence suggests that in the "double empathy problem model, autistic people have a unique interaction style which is significantly more readable by other autistic people, compared to non-autistic people."

=== Restricted and repetitive interests and behavior === People with Asperger syndrome can display behavior, interests, and activities that are restricted and repetitive and are sometimes abnormally intense or focused. They may stick to inflexible routines, move in stereotyped and repetitive ways, preoccupy themselves with parts of objects, or engage in compulsive behaviors like lining objects up to form patterns. The pursuit of specific and narrow areas of interest is one of the most striking among possible features of AS. Individuals with AS may collect volumes of detailed information on a relatively narrow topic such as weather data or star names without necessarily having a genuine understanding of the broader topic. For example, a child might memorize camera model numbers while caring little about photography. This behavior is usually apparent by age five or six. Although these special interests may change from time to time, they typically become more unusual and narrowly focused and often dominate social interaction so much that the entire family may become immersed. Because narrow topics often capture the interest of children, this symptom may go unrecognized. Stereotyped and repetitive motor behaviors, called stimming, are a core part of the diagnosis of AS and other ASDs. Stims are believed to be used for self-soothing and regulate sensory input. They include hand movements such as flapping or twisting, and complex whole-body movements. These are typically repeated in longer bursts and look more voluntary or ritualistic than tics, which are usually faster, less rhythmical, and less often symmetrical. Stimming may have a connection with tics, and studies have reported a consistent comorbidity between AS and Tourette syndrome in the range of 8–20%, with one figure as high as 80% for tics of some kind or another, for which several explanations have been put forward, including common genetic factors and dopamine, glutamate, or serotonin abnormalities. According to the Adult Asperger Assessment (AAA) diagnostic test, a lack of interest in fiction and a positive preference towards non-fiction is common among adults with AS.

=== Speech and language === Although individuals with Asperger syndrome acquire language skills without significant general delay and their speech typically lacks significant abnormalities; language acquisition and use is often atypical. Abnormalities include verbosity, abrupt transitions, literal interpretations and miscomprehension of nuance, use of metaphor meaningful only to the speaker, auditory perception deficits; unusually pedantic, formal, or idiosyncratic speech; and oddities in loudness, pitch, intonation, prosody, and rhythm. Echolalia has also been observed in individuals with AS. Three aspects of communication patterns are of clinical interest: poor prosody, tangential and circumstantial speech, and marked verbosity. Although inflection and intonation may be less rigid or monotonic than in classic autism, people with AS often have a limited range of intonation: speech may be unusually fast, jerky, or loud. Speech may convey a sense of incoherence; the conversational style often includes monologues about topics that bore the listener, fails to provide context for comments, or fails to suppress internal thoughts. Individuals with AS may fail to detect whether the listener is interested or engaged in the conversation. The speaker's conclusion or point may never be made, and attempts by the listener to elaborate on the speech's content or logic, or to shift to related topics, are often unsuccessful. Children with AS may have a sophisticated vocabulary at a young age and such children have often been colloquially called "little professors" but have difficulty understanding figurative language and tend to use language literally. Children with AS appear to have particular weaknesses in areas of nonliteral language that include humor, irony, teasing, and sarcasm. Although individuals with AS usually understand the cognitive basis of humor, they seem to lack understanding of the intent of humor to share the enjoyment with others. Despite strong evidence of impaired humor appreciation, anecdotal reports of humor in individuals with AS seem to challenge some psychological theories of AS and autism.

=== Motor and sensory perception === Individuals with Asperger syndrome may have signs or symptoms that are independent of the diagnosis but can affect the individual or the family. These include differences in perception and problems with motor skills, sleep, and emotions. Individuals with AS often have excellent auditory and visual perception. Children with ASD often demonstrate enhanced perception of small changes in patterns such as arrangements of objects or well-known images; typically this is domain-specific and involves processing of fine-grained features. Conversely, compared with individuals with high-functioning autism, individuals with AS have deficits in some tasks involving visual-spatial perception, auditory perception, or visual memory. Many accounts of individuals with AS and ASD report other unusual sensory and perceptual skills and experiences. They may be unusually sensitive or insensitive to sound, light, and other stimuli; these sensory responses are found in other developmental disorders and are not specific to AS or to ASD. There is little support for increased fight-or-flight response or failure of habituation in autism; there is more evidence of decreased responsiveness to sensory stimuli, although several studies show no differences. Hans Asperger's initial accounts and other diagnostic schemes include descriptions of physical clumsiness. Children with AS may be delayed in acquiring skills requiring dexterity, such as riding a bicycle or opening a jar, and may seem to move awkwardly or feel "uncomfortable in their own skin". They may be poorly coordinated or have an odd or bouncy gait or posture, poor handwriting, or problems with motor coordination. They may show problems with proprioception (sensation of body position) on measures of developmental coordination disorder (motor planning disorder), balance, tandem gait, and finger-thumb apposition. There is no evidence that these motor skills problems differentiate AS from other high-functioning ASDs. Children with AS are more likely to have sleep problems, including difficulty in falling asleep, frequent nocturnal awakenings, and early morning awakenings. AS is also associated with high levels of alexithymia, which is difficulty in identifying and describing one's emotions. Although AS, lower sleep quality, and alexithymia are associated with each other, their causal relationship is unclear.

== Causes ==

Hans Asperger described common traits among his patients' family members, especially fathers, and research supports this observation and suggests a genetic contribution to Asperger syndrome. Although no specific genetic factor has yet been identified, multiple factors are believed to play a role in the expression of autism, given the variability in symptoms seen in children. Hundreds of genes have been linked to AS, and these genes play crucial role in a multitude of biological processes, exerting influence over the maturation and functioning of the brain. Evidence for a genetic link is that AS tends to run in families where more family members have limited behavioral symptoms similar to AS (for example, some problems with social interaction, or with language and reading skills). Most behavioral genetic research suggests that all autism spectrum disorders have shared genetic mechanisms. There may be shared genes in which particular alleles make an individual vulnerable, and varying combinations result in differing severity and symptoms in each person with AS. A few ASD cases have been linked to exposure to teratogens (agents that cause birth defects) during the first eight weeks from conception. Although this does not exclude the possibility that ASD can be initiated or affected later, it is strong evidence that ASD arises very early in development. Many environmental factors have been hypothesized to act after birth, but none has been confirmed by scientific investigation. These environmental elements can act as independent and significant risk factors, or they can potentially influence pre-existing genetic factors in people who have a genetic predisposition.

== Mechanism ==

Asperger syndrome appears to result from developmental factors that affect many or all functional brain systems, as opposed to localized effects. Although the specific underpinnings of AS or factors that distinguish it from other ASDs are unknown, and no clear pathology common to individuals with AS has emerged, it is still possible that AS's mechanism is separate from other ASDs. Neuroanatomical studies and the associations with teratogens strongly suggest that the mechanism includes alteration of brain development soon after conception. Abnormal fetal development may affect the final structure and connectivity of the brain, resulting in altered neural circuits controlling thought and behavior. Several theories of mechanism are available; none are likely to provide a complete explanation.

=== General-processing theories === One general-processing theory is weak central coherence theory, which hypothesizes that a limited ability to see the big picture underlies the central disturbance in ASD. A related theory—enhanced perceptual functioning—focuses more on the superiority of locally oriented and perceptual operations in autistic individuals.

=== Mirror neuron system (MNS) theory ===

The mirror neuron system (MNS) theory hypothesizes that alterations to the development of the MNS interfere with imitation and lead to Asperger syndrome's core feature of social impairment. One study found that activation is delayed in the core circuit for imitation in individuals with AS. This theory maps well to social cognition theories like the theory of mind, which hypothesizes that autistic behavior arises from impairments in ascribing mental states to oneself and others; or hyper-systemizing, which hypothesizes that autistic individuals can sy...

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Neuroscience - Neuroscience