Motnja v razvoju avtizma

Avtizem, ki mu pravimo tudi klasični avtizem ali avtistična motnja, razvojna motnja, ki vpliva na telesne, socialne in jezikovne spretnosti, s pojavom znakov in simptomov, običajno pred tremi leti. Izraz avtizem (iz grško autos, kar pomeni "jaz") je leta 1911 uvedel švicarski psihiater Eugen Bleuler, ki ga je uporabil za opis umika v notranji svet, pojav, ki ga je opazoval pri osebah s shizofrenijo. Uporaba besede avtizem za opis stanja, kakršno je danes znano, je nastala leta 1943, ko je ameriški psihiater Leo Kanner, rojen v Avstriji, razlikoval od shizofrenije.

Razvrstitev in pojavnost

Klasični avtizem, Aspergerjev sindrom in pervazivna razvojna motnja, ki niso drugače določeni (PDD-NOS), so vključeni v sklop motenj, ki jih običajno imenujemo motnje avtističnega spektra (ASD). Za razliko od klasičnega avtizma posamezniki z Aspergerjevim sindromom običajno nimajo večjih kognitivnih težav, njihov IQ pa je v normalnem ali celo visokem razponu. Poleg tega ne izkazujejo zamude pri pridobivanju jezika. Posamezniki z PDD-NOS kažejo nekatere, vendar ne vse enake znake in simptome kot klasični avtizem.

Ameriški centri za nadzor bolezni (CDC) so ocenili, da ASD vplivajo na območje približno med 1 na vsakih 45 in 1 na vsakih 68 otrok v Združenih državah Amerike. V Združenem kraljestvu je šolsko populacijsko študijo, objavljeno leta 2009, razširjenost ocenjevala na približno 1 na vsakih 100 otrok. V obeh državah samci prizadenejo štiri do petkrat pogosteje kot samice.

Medtem ko so bile določene najboljše ocene, se pojavnost avtizma med državami in znotraj njih močno razlikuje, kar je deloma posledica razlik v virih in kliničnih opredelitev, uporabljenih za diagnozo. Na primer, v eni regiji Združenega kraljestva je bilo približno 1 od vsakih 185 posameznikov prizadetih zaradi ASD. Vendar pa je bilo v istem predelu države ugotovljeno, da je pri klasičnem avtizmu pojavnost med 1 od 250 in 1 od 400 posameznikov. Poleg tega se zdi, da se je svetovna pojavnost avtizma med sredino 1900 in začetkom 2000-ih močno povečala. Ni pa znano, ali je prišlo do resnega povečanja pojavnosti motnje, saj bi lahko prišlo do uporabe širših diagnostičnih meril ali drugih dejavnikov. V ZDA npr.nacionalna zdravstvena anketa (NHIS) je ena izmed več različnih metod nadzora, ki se uporabljajo za določanje razširjenosti ASD. Leta 2014 so bile spremembe v vprašanjih NHIS glede ASD, vključno s preoblikovanjem besedil in razširitvijo za podrobnejše podrobnosti, povezane s poznejšim povečanjem diagnoz ASD pri starših, ki so jih poročali starši.

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.