There is a difference between using the word autism and the term autism spectrum disorder. Autism itself describes any one of the 5 different types of pervasive developmental disorders. These pervasive developmental disorders essentially come under the autism disorder spectrum. There are conflicting theories about how the five disorders relate to one another.

While some researchers argue that they are all separate disorders with similar symptoms, others promote the theory that autism is really a spectrum. According to this theory, on one end of the autism disorder spectrum, there are the mild cases, with symptoms that are hardly noticeable. On the other end, cases can be so severe such that the person inflicted cannot cope with normal functioning and living independently.

Autism is a chronic brain disorder that manifests in developmental difficulties in the areas of social interaction, verbal skills and communication. It is usually detected after the child turns three years old. However, in certain cases, symptoms may also be detected when your child turns one.

If your child is autistic, he is likely to have repetitive and narrow interests. He will not be willing to try new things or food, preferring to always stick to the same ones that he is used to. Also, he finds it hard to cope with changes in schedules and environment. He can react violently when any change should occur or if there is a disruption to his normal schedule of activities. His behavior is odd and unpredictable. You may even think that he is being naughty, without realizing that he is actually having a brain disorder difficulty.

There are conflicting opinions about what causes autism. Some scientists and researchers believe that it is a genetic abnormality. Yet others think that it is caused by an injury to the brain or exposure to an environmental toxin. The latter view is supported by the fact that in some population areas, autism is at higher rates of incidence than it is elsewhere.

You may start observing some developmental problems of your child between the ages of 12 and 36 months old. It may be that your child is not hitting some milestones with underdeveloped or delay in speech and communication skills. You may also begin to notice that he tends to keep himself or if he has little awareness of social cues. His eye contact is poor and he cannot focus clearly. However, if your child only has mild autism, you may not be able to detect that anything is wrong until he goes to school. In some cases, your child may go undiagnosed until he is much older when social and communication skills are required.

If you have an autistic child, you may fear that his disorder may become worse over the years. However, there is no cause for concern apparently. Research shows that autism is non-progressive, meaning that it does not get worse in time.

Here is a breakdown of what comes under autism disorder spectrum or otherwise known as the 5 pervasive developmental disorders:

1. Autism. Symptoms can be recognized before a child turns 3-years-old. However, they may be more obvious much later than this. If your child is diagnosed with autism he will have difficulty making or maintaining eye contact, have impaired social functioning, can be overwhelmingly absorbed with himself and would seem like a loner.

2. Asperger Syndrome. Asperger Syndrome is similar to autism in that it tends to show up before your child turns 3 years old. However, your child will be able to function at a higher level than an autistic child. He can still have problems with social functioning, communication and speech. He will also have narrowly defined interests. But with some therapy and help, most asperger children are able to live independently when they get older.

3. Rex syndrome. Doctors cannot agree whether Rex syndrome is a type of autism or not. This syndrome almost exclusively afflicts girls. Usually your child will develop normally for 6 to 18 months and then all of a sudden, show a loss of skills in such areas as speech and lose the ability to control her hands and her feet. This syndrome can be tested for with an 80% accuracy rate.

4. Childhood disintegrative disorder (CDD). CDD takes place a little later. It happens anytime between the age of 2 to 4 years old. You would notice a marked degeneration in social, physical, mental and verbal skills. The long period of normal development below the age of 2 is the distinguishing factor between autism and CDD.

5. Pervasive developmental disorder. This disorder applies if your child is not within any of the above other 4 mentioned categories. He is diagnosed with a pervasive developmental disorder if he is found to have impairments in social interaction, stereotyped behavior and communication but with symptoms not otherwise defined.