Autism is a developmental disability that causes problems with social skills and communication. Autism can be mild or severe, and not all behaviors will exist in every child. Some individuals on the autism spectrum do not speak, while others love to talk but have difficulty with conversational speech and/or understanding the nuances of language and nonverbal cues when talking to others.
In terms of speech development, signs of symptoms of Autism are as follows:
-Not speaking or very limited speech;
-Loss of words the child was previously able to say;
-Difficulty expressing basic wants and needs;
-Poor vocabulary development;
-Repeating what is said (echolia);
-Problems answering questions; and
-Speech that sounds different (e.g. "robotic" speech or speech that is high-pitched).
Speech-language therapy is designed to coordinate the mechanics of speech with the meaning and social use of language. Speech-language pathologists (SLPs) play a key role is diagnosing autism because problems with speech are often the first signs of autism, and should be consulted early in the evaluation process. From this evaluation, the SLP will set goals to help the person communication more useful and functional ways. These goals may include mastering spoken language and/or learning nonverbal communication skills like signs and gestures.
In 2006, ASHA (the American Speech-Language-Hearing Association) developed four documents delineating the role of SLPs in working with individuals with autism, as well as what is needed in terms of knowledge and skills to serve this population. The documents can be found here: http://www.asha.org/public/speech/disorders/Autism.htm.