Autism is a complex developmental disability that typically appears during the first three years of a child\’s life. It is the result of a neurological disorder that profoundly affects the functioning of the brain. It is estimated to occur in as many as 1 in 500 individuals. Autism is 4 times more prevalent in boys than girls. Its prevalence rate now places it as the 3rd most common developmental disability more common than Down Syndrome. Autism is often referred to as a spectrum disorder, which means that the symptoms of autism can occur in many combinations and may range from mild to severe. Children with autism often look normal, but seem to be withdrawn into their own world.
Individuals with autism find it hard to communicate with others and relate to the outside world. Aggression and self-injurious behavior may also be present. Other behaviors exhibited may include repeated body movements (such as rocking and hand flapping), unusual responses to people or attachments to objects and resistance to changes and routines. Individuals with autism may experience sensory problems in the 5 senses of sight, touch, hearing, smell and taste. Although a single cause of autism has not yet been found, recent research links autism to biological or neurological differences in the brain. In many families, there appears to be a pattern of autism or related disability suggesting a genetic basis to the disorder (1)
Causes:

Autism has no single identifiable cause but seems to be a result of a neurobiological disorder that profoundly affects the functioning of the brain. Studies of people with autism have found abnormalities in several regions of the brain including the cerebellum, amygdala, hippocampus, septum and mamillary bodies. Neurons in these regions appear smaller than normal and have stunted nerve fibers which may interfere with nerve signaling. These abnormalities suggest that autism results from disruption of normal brain development early in fetal development. Other studies suggest abnormalities of serotonin or other signaling molecules in brain.(2)
Twin and family studies suggest that genetic factors play a substantial causal role.(4) In the past 5 years genetic advances have identified some candidate genes in some families but it is thought that autism is a complex genetic disorder and may involve as many as 5-15 genes working in combination to produce the disorder, or may involve the influence of environmental factors.(3)
Also prenatal exposure to valproic acid, thalidomide and alcohol has been associated with an increased risk of autism.(4)
Autism also seems to occur more frequently in children who have other medical conditions including fragile X-syndrome, tuberous sclerosis, untreated phenylketonuria and congenital rubella syndrome. In recent years, some news reports have raised concerns about a connection between autism and vaccines (MMR) containing thimerosal , a preservative that contains a very small amount of mercury. However extensive reports from the American Institute of Pediatrics, the Institute of Medicine and the Centre for Disease Control and Prevention conclude that there is no scientifically proven link between these vaccines and autism.(5)
Symptoms and signs:

Autism is one of five conditions referred to as autism spectrum disorders or pervasive developmental disorders (PDD). These five conditions have different signs:
1-Autism: Children with autism exhibit a wide range of problems with varying degrees of severity. In general, they have problems in three crucial areas of development ? social skills, language and behaviour. The most severe cases of autism are marked by repetitive and unusual behaviours, sometimes including self-injurious and aggressive behaviours. Children with autism may require lifelong care and supervision, depending on the severity of their condition.
2-Asperger’s syndrome.: People with Asperger’s syndrome usually have average intelligence and normal language development, but impaired social skills and awkward movements. Others often see them as odd or eccentric.
Some researchers believe both Albert Einstein and Isaac Newton may have had Asperger syndrome. The researchers pointed out that Einstein was a loner as a child and often repeated sentences obsessively until he was seven years old. His career was centered on complex mathematical topics. He gave very confusing lectures.
As for Newton, the researchers noted that he hardly spoke, had few friends and was often bad-tempered around them. He often became so engrossed in his work (the science of physics) that he forgot to eat. He always gave his scheduled lectures, even if no one came.(6)
3-Childhood disintegrative disorder (CDD). Children with this rare condition develop normally during their early years before losing many of their language and social skills after age 3. Children with CDD may also show other signs of autistic behaviour.
4-Rett syndrome. This very rare genetic disorder affects only girls. It causes them to develop autism-like behaviours after seemingly normal early development.
5-Pervasive developmental disorder not otherwise specified (PDD-NOS). This term applies to children with some signs of autism, but not enough to be diagnosed with the classic form of the disorder.
Two children with the same diagnosis may act quite differently and have strikingly different skills. If a child has any of these autism spectrum disorders, he or she may develop normally for the first few months ? or years ? of life, then become less responsive to other people, including you. You may recognize the following signs in the areas of social skills, language and behaviour:
Social skills:
Fails to respond to his or her name
Has poor eye contact
Appears not to hear you at times
Resists cuddling and holding ? screams to be let down
Appears unaware of others’ feelings
Seems to prefer playing alone ? retreats into his or her “own world”
Language:
Starts speaking later than other children
Loses previous ability to say words or sentences
Speaks with an abnormal tone or rhythm ? may use a singsong voice or robot-like speech
Can’t start a conversation or keep one going
May repeat words or phrases verbatim, but doesn’t understand how to use them
Behaviour:
Performs repetitive movements, such as rocking or hand-twisting
Develops specific routines or rituals
Becomes disturbed at the slightest change in routines or rituals, such as if you move objects that your child has lined up
Hyperactive
May be fascinated by parts of an object, such as the spinning wheels of a toy car
May be sensitive to sensory stimulation, such as light, sound and touch
Children with autism also show signs of poor joint attention ? or shared attention ? at a young age. Joint attention is an early-developing social skill in which two people ? usually a young child and an adult ? share the experience of looking at an object or observing an event. It includes the ability to point at objects and follow another person’s gaze. This skill is crucial to later language and social development.
In some children with autism, problems improve as they mature. Some people, usually those with the least severe impairments, eventually may lead normal or near-normal lives. For other people, however, there’s little improvement in language or social skills, and the adolescent years can mean a worsening of behaviour problems.
The majority of children with autism also have mental retardation, which means they’re slow to acquire new knowledge or skills. However, some children with autism have normal to high intelligence. These children learn quickly yet have trouble communicating, applying what they know in everyday life, and adjusting in social situations. An extremely small number of children with autism are “autistic savants,” which means they have exceptional skills in a specific area, such as art or math.(5)