Stuttering is an interruption in the fluency of verbal expression. It is a complaint that has been known for centuries and occurs in all cultures and ethnic groups. Stuttering is symptom, not a disease, but the word stuttering is usually used for both the symptom and the disorder which causes it.

The development of stuttering commonly occurs before puberty, between two and five years of age. The technical term is persistent developmental stuttering (PDS). There is also acquired or neurogenic stuttering, which occurs after brain damage. The neurogenic sufferer may have had a stroke or head trauma before acquiring a stutter.

PDS is usually most noticeable at the beginning of a phrase, word or complex sentence. Associated with this is the anxiety the sufferer feels, which tends to elevate the problem. However, at repeated readings of the same material, the frequency of stuttering tends to decline due to adaptation and consistency.

PDS is a very common disorder. Around 1% of the population suffer from the complaint, including an estimated three million people in the United States and a total of 55 million worldwide. There is no difference based on social class, and stuttering can severely hinder communication to cause very serious social problems for the individual. Stuttering may be an inherited problem passed on from generation to generation.

The recovery rates for a PDS sufferer are about 80%, and the recovery rate is considerably more frequent in girls than in boys. It is not clear to what extent recovery depends on the efforts of the patient as opposed to the help of speech therapists, who use breathing techniques to help patients overcome the stuttering. Also, there is no way of predicting whether an affected child will recover from the complaint or not.

There are many different theories about the origin of stuttering and its corresponding treatment. Some regard it as a learned behavior resulting from an unhappy home life and the way a parent reacts towards a child's problems. The severity of the problem is clearly made worse by arousal, nervousness and embarrassment, although some brave stutterers have treated their own problem by putting themselves on the spot in front of a large audience, only to find the problem vanish when they confront it head on.

Recent scientific findings from brain scans have shown that stutterers have slight abnormalities in complex coordination tasks. This suggests that the underlying problems are to be found around motor and associated premotor brain areas. As brain scans become more and more sophisticated, it is hoped that more information will become available regarding language areas of the brain and the causes of stuttering.