Many disorders can affect our ability to speak and communicate. They range from saying sounds incorrectly to being completely unable to speak or understand speech. Causes include

• Hearing disorders and deafness
• Voice problems, such as dysphonia or those caused by cleft lip or palate
• Speech problems like stuttering
• Developmental disabilities
• Learning disorders
• Autism spectrum disorder
• Brain injury
• Stroke

Some speech and communication problems may be genetic. Often, no one knows the causes. By first grade, about 5 percent of children have noticeable speech disorders. Speech and language therapy can help.

NIH: National Institute on Deafness and Other Communication Disorders