One crucial piece of information is that there is no biological marker of autism. This means that a doctor cannot do a blood test as one might with diabetes, for example, or ‘see’ the disability on a chromosome like one can with Down’s Syndrome. The nature of the diagnosis of autism is different in that it comes down to a trained professional’s best judgment in conjunction with the DSM criteria (see #1) and other standardized questionnaires or tests. This trained professional is sometimes a licensed clinical psychologist or a pediatrician however it is good to ask what the person’s training consists of in regard to autism.
If you are suspicious about whether your son or daughter may have an autism spectrum disorder, the best thing to do is to watch for signs consistent with those three indicators described above: regression of language ability, repetitive or ritualistic behavior, and seemingly odd social interactions. Observe your child closely under a number of different contexts, conditions, and environments. Also note how your child compares with his or her peers. At the same time, it is important to focus on these three areas only and also to consider them as a whole. For example, although individuals with autism sometimes engage in challenging behavior such as tantrums, it does not mean that tantrums (even those that appear to be on the severe side for a 2-3 year old) should cause you to think that your child may have autism; especially if they do not present with any of the three defining characteristics. The bottom line is that if you suspect your child is not developing in these areas as a child their age should be, it is best to seek out a trained professional in order to complete a formal assessment.