Although the cause of speech and language problems in autism is unknown, many experts believe that the difficulties are caused by a variety of conditions that occur either before, during, or after birth affecting brain development. This interferes with an individual's ability to interpret and interact with the world. Some scientists tie the communication problems to a "theory of mind" or impaired ability to think about thoughts or imagine another individual's state of mind. Along with this is an impaired ability to symbolize, both when trying to communicate and in play.
[source: NICHD, http://www.nidcd.nih.gov/health/voice/autism.asp]
