These delays and disorders range from simple sound substitutions to the inability to understand or use language or use the oral-motor mechanism for functional speech and feeding. Some causes of speech and language disorders include hearing loss, neurological disorders, brain injury, mental retardation, drug abuse, physical impairments such as cleft lip or palate, and vocal abuse or misuse. Frequently, however, the cause is unknown. Incidence More than one million of the students served in the public schools' special education programs in the 1996-97 school year were categorized as having a speech or language impairment. Language disorders may be related to other disabilities such as mental retardation, autism, or cerebral palsy.
Speech disorders refer to difficulties producing speech sounds or problems with voice quality.
They might be characterized by an interruption in the flow or rhythm of speech, such as stuttering, which is called dysfluency. Speech disorders may be problems with the way sounds are formed, called articulation or phonological disorders, or they may be difficulties with the pitch, volume or quality of the voice. There may be a combination of several problems. People with speech disorders have trouble using some speech sounds, which can also be a symptom of a delay. Listeners may have trouble understanding what someone with a speech disorder is trying to say.