If you’re looking for some basic information on adolescent speech or language impairment then check out this informative article at Disabled World. The article outlines the definition of a speech or language impairment, the difference between speech and language, the education of speech-language pathologists and a few basic facts on speech/language impairments.
The article is quick to point out that there is no proven origin for Speech Language Impairment (SLI) but that 50-70% of children with SLI have at least one family member who also has SLI. The condition first appears in young children and may persist into adulthood without early identification and intervention. Parents of children with SLI can equip their child for success by the time their child is age three or four, leading to positive experiences for their child in kindergarten.