These causes are certainly varied, as they reflect the diversity of people with autism and, of course, affect common pathophysiological and neuropsychological mechanisms necessary for autism to occur.

These mechanisms are, in turn, influenced by a variety of personal and environmental factors, leading to a range of variations in core clinical manifestations. Given that autism is essentially a developmental disorder, its exact presentation varies significantly depending on age and experience. Clinical diagnosis should serve as a marker for development rather than a negative label and should lead to the recognition of each individual's specific abilities and needs.

What is Known About the Cause(s)?

Autism is a congenital brain disorder that affects the way the brain processes information. The cause remains unknown. Some studies suggest a neurological problem affecting those parts of the brain that process language and sensory information. There may be an imbalance of certain neurochemicals in the brain. The exact cause or causes have yet to be determined. It is clear that there is no single biological cause, and the etiology should be considered multifactorial. Genetic factors may sometimes be involved. Specifically, the fragile X chromosome, PKU, and NFI chromosomes are implicated. Twin studies suggest that 3 to 5 genes are responsible for the manifestation of autism, and researchers are examining chromosomes 7, 9, and 15. However, genes alone cannot explain the entire range of early deviations. In other cases, birth trauma or the existence of a strong association between autism spectrum disorders and medical conditions with a genetic basis (e.g., phenylketonuria, tuberous sclerosis, neurofibromatosis...) are implicated.

The evidence supporting a biological organic etiological mechanism for autism is now overwhelming. Ultimately, autism may result from a combination of various causes.

It has been proven, beyond any doubt, that there is no causal link between parents' attitudes and actions and the development of an autism spectrum disorder.

The clinical expression should be considered the result of the interaction between an individual's constitution (biological predisposition) and a series of internal and external factors that can interact in a favorable way, providing protection against risk, or in an unfavorable way, increasing risk and the consequent clinical expression. Protective factors may include maintaining a higher intellectual potential, developing language and speech, a cheerful temperament, successful developmental interventions, and a supportive social environment that can cope with many challenges while encouraging development. Conversely, risk factors include lower intellectual potential, lack of language or speech, neurological deficits, comorbidity with psychiatric conditions, absence of early and appropriate educational programs, and a social environment unable to withstand and cope with the enormous pressure caused by the presence of a child with an autism spectrum disorder.