Autism is a neurodevelopmental disorder with onset in early childhood. Given the variety of symptoms and its clinical complexity, it is more appropriate to speak of Autism Spectrum Disorders (ASD). In terms of nosological classification, in the DSM-IV the disorder comes under the category of “Pervasive Developmental Disorders”, among various other syndromes, including Asperger’s syndrome, Rett syndrome and childhood disintegrative disorder.
Epidemiology and Aetiology
The incidence varies from 5 to 50 people out of 10,000 , depending on the diagnostic criteria. Autism Spectrum Disorders predominantly affect males , with a rate two to four times higher than in women , it almost always occurs within the first 3 years of life. Studies conducted in general populations in various parts of the world, without regard to the exclusion criteria or differential diagnoses, can reliably detect prevalence of approximately 1% in all age groups .
The causes of autism are still unknown . In the past, it was believed that autism was influenced by environmental conditions, such as growing up with “cool parents” with an attitude of rejection, or maybe due to brain damage. It appeared that the genetic component was not important, because there were no reported cases of parents with autistic children who also had autism, and that the risk for siblings was only 3-6%  . This, however, is an estimate of 100 times larger than that of the general population (which corresponds to 0.03%), and this difference, therefore, implies a strong familiarity. The first systematic study of twins , modified the idea that it was a disorder of environmental origin: 4 out of 11 pairs of identical twins concordant for autism manifested the disorder, while none of the 10 pairs of fraternal twins had autism. These levels of concordance of 35% and 0%, rose to 82% and 10% when the diagnosis was extended to
cognitive disorders. These findings were subsequently replicated by other studies of twins  , resulting in a conservative estimate of concordance in monozygotic twins of 60%.
Today autism is considered a one of the most heritable mental disorders . Furthermore, a study of international collaboration has demonstrated the existence of an association with a locus on chromosome 7 (7q31-33) . Other findings have also been reported for chromosome 13  and 15 .
Symptoms and neuropsychological profile
According to the DSM-IV, the salient features of autism are:
– The presence of difficulties in social interaction
– Difficulties in communication
– Limited activities and interests
The majority of children with autism present :
– Mental retardation = 80% with IQ < 70. Some people might excel in particular areas (mathematics, music, and mechanics), but other people suffer from serious mental retardation.
– Lack of motivation to learn new tasks and participate in social and academic activities. Since these children often fail in simple activities, they tend to avoid engaging, and do not experiment with new things. Another characteristic is the lack of attachment to caregivers: when they get hurt, they do not ask for help, do not show sorrow when parents go away, and do not show any emotion on their return.
– Ultra stimulus selectivity = inability to use tips from the environment. They answer a to a few stimuli, and this interferes significantly on learning, and in the ability to generalize learned behaviours and take advantage of the normal application procedures (verbal or facial expressions).
– Severe difficulties in acquiring a communicative language = when language is present it is characterized by some deficit: echolalia; incorrect use of pronouns (“you” instead of “me”); disprosodia with indifference; morpho-syntactic structure of the sentence resulting in poor and distorted sentences, acquisition of the lexicon linked to the context acquisition and not generalized.
– Compulsive ritualistic behaviour in ordering objects, preference for certain foods or clothes, fixation on certain objects that they need to bring with them wherever they go. Changes in routine provoke dramatic actions and catastrophic consequences.
– Unusual response to their environment = visual and auditory sensory deficit more apparent than real. The motor stereotypes are an expression of a sensory feedback or a vestibular deficit.
– Inadequate expression of their emotions = poor or excessive answers, at the wrong time, unintelligible fears or laughter apparently unmotivated.
In addition, autism can be associated with several other psychiatric symptoms, such as inattention, hyperactivity, aggressiveness, anxiety, depression, which in some cases may lead to additional diagnoses.
In conclusion, the most relevant and marked aspects of this disorder can be seen as the poor or total lack of interest in people and in the lack of emotions, resulting in a reduction in mentalisation, i.e. the behaviours and thoughts that make us “social animals”. Autism can be explained psychologically as the impaired ability to empathize, or model, the mental states governing the behaviour of other people. Alternatively, autism often results in a higher degree systemisation, i.e. to infer the rules governing the behaviour of objects and of the inanimate environment .
The main phenotypic characteristics of the autistic spectrum, therefore, bring patients to show behaviours that are more oriented towards themselves, and showing an impairment of cognition and social behaviour, as well as an increase in “mechanistic cognition (which refers to giving greater attention to the physical world)” .
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