Нарушение развития аутизма

Аутизм, также называемый классическим аутизмом или аутичным расстройством, расстройством развития, влияющим на физические, социальные и языковые навыки, с появлением признаков и симптомов, как правило, в возрасте до трех лет. Термин аутизм (от греческого autos, означающий «я») был введен в 1911 году швейцарским психиатром Юдженом Блейлером, который использовал его для описания отвлечения во внутренний мир, феномен, который он наблюдал у людей с шизофренией. Использование слова «аутизм» для описания состояния, как оно известно сегодня, возникло в 1943 году, когда американский психиатр австрийского происхождения Лео Каннер отделил расстройство от шизофрении.

Классификация и заболеваемость

Классический аутизм, синдром Аспергера и распространенное расстройство развития, не указанные иным образом (PDD-NOS), все включены в общий список расстройств, обычно называемых расстройствами аутистического спектра (ASDs). В отличие от классического аутизма, люди с синдромом Аспергера обычно не имеют серьезных когнитивных проблем, и их IQ находится в нормальном или даже высоком диапазоне. Кроме того, они не показывают задержки в овладении языком. Люди с PDD-NOS демонстрируют некоторые, но не все те же признаки и симптомы, что и классический аутизм.

По оценкам Центров по контролю за заболеваниями США (CDC), расстройства аутистического спектра влияют примерно на 1 из каждых 45 и 1 на каждые 68 детей в Соединенных Штатах. В Соединенном Королевстве, опубликованное в 2009 году исследование населения в школах, по оценкам, распространенность составляла примерно 1 на каждые 100 детей. В обеих странах мужчины болеют в четыре-пять раз чаще, чем женщины.

While best estimates have been determined, the incidence of autism varies significantly between and within countries, which is partly due to differences in resources and the clinical definitions used for diagnosis. For example, in one region of the United Kingdom, roughly 1 in every 185 individuals was found to be affected by an ASD. However, in the same region of the country, classic autism was found to range in incidence between 1 in 250 and 1 in 400 individuals. In addition, there appears to have been a dramatic increase in the global incidence of autism between the mid-1900s and the early 2000s. However, it is not known whether there has been a true increase in the incidence of the disorder, since the increase could be due to the use of broader diagnostic criteria or other factors. In the United States, for example, the National Health Interview Survey (NHIS) is one of several different surveillance methods used to determine ASD prevalence. In 2014 changes in NHIS questions about ASD, including rewording and expansion for greater detail, were associated with a subsequent increase in parent-reported diagnoses of ASDs in children.

Possible causes and risk factors

The cause of autism remains unclear. However, it appears that both genetic and environmental factors contribute to the disorder. A study published in 2011 that assessed pairs of twins in which at least one twin was affected by an ASD suggested that, while genetic factors contribute moderately to susceptibility, environmental factors contribute to a greater degree. Other research has indicated that genetic vulnerability to autism differs between males and females, with more mutations being needed to produce the condition in females compared with males. Increased genetic resiliency to autism in females lends support to the so-called female protective model, which attempts to explain the increased prevalence of autism in males. Interactions between genes and the environment likely play an important role in influencing susceptibility to autism.

An environmental risk factor that has been proposed for autism and other ASDs is maternal infection during pregnancy. Indeed, certain maternal infections have been associated with an increased incidence of neurodevelopmental disorders (e.g., schizophrenia and autism) in offspring. Infection with agents such as the rubella virus activate the mother’s immune system, and such immunological activity in the early stages of pregnancy has been linked with damage to the developing brain of the embryo or fetus.

Other environmental factors associated with increased risk of autism include maternal use of certain antidepressants (namely SSRIs, or selective serotonin reuptake inhibitors) during pregnancy and maternal and paternal age at the time of conception. A study of more than 4.9 million births that took place in the U.S. state of California between 1990 and 1999 revealed that about 5 percent of the nearly 12,160 children who later developed autism were born to older mothers. Mothers 40 years or older had the highest risk of giving birth to a child who would later develop autism. In contrast, older paternal age was a risk factor only when maternal age was 30 or younger. The underlying reasons for those associations, however, were unclear.

Sibling studies have revealed valuable information about the heritable nature of autism. For example, scientists found that a region on chromosome 15 is deleted or duplicated in some children with autism; defects in and near this region have been implicated in other disorders associated with neurobiological development, including Angelman syndrome, Prader-Willi syndrome, and epilepsy.

Another proposed cause of autism emerged in 1998, when a paper published in the scientific journal The Lancet suggested an association between childhood vaccination and autism. This suggestion quickly developed into a controversial issue between parents and the scientific community. However, scientific evidence collected from extensive studies investigating the proposed association did not support a causal relationship. Further investigations revealed that the 1998 paper had violated research ethics and contained false claims, and thus in 2010 it was retracted by the journal.

Signs and symptoms

The signs and symptoms of autism are variable, ranging from mild to moderate to severe in nature. There are three major categories of signs and symptoms: (1) abnormalities in social interaction; (2) abnormalities in communication; and (3) abnormalities in behaviours, interests, and activities, which are usually restricted and repetitive. Social communication problems include a narrow range of facial expressions, poor eye contact during interactions, and difficulty establishing relationships with peers. This may result in a decreased quality of their relationships and can lead to social avoidance when severely affected. Communication problems include delayed or lack of spoken language, poor conversation skills, lack of appropriate developmental play, and diminished gestures. Repetitive behaviour problems include stereotyped motor mannerisms, such as hand flapping, restricted interests, inflexible adherence to routines, and a preoccupation for parts of objects. For example, a child with autism may play with the wheels of a toy car instead of using the car in the proper manner as a vehicle. Some children become obsessed with specific objects such as buttons and sometimes form deep attachments to these objects. In addition, disruption of routines and schedules or familiar surroundings may cause agitation and tantrums.

About 70 percent of children with autism exhibit abnormal eating behaviours as well, which can include extreme sensitivity to food textures and very narrow food preferences. Affected children, for example, may favour foods of a particular colour or may select only grains. These behaviours may be apparent as early as one year of age.