Communication disorders are conditions that impair a person’s ability to speak or to understand language. These conditions are typically diagnosed during childhood. In some cases, patients may experience relatively mild impairments, such as a tendency to make errors in sound when speaking (e.g., lisping) or an inability to comprehend certain parts of language. In other cases, patients may experience a total loss of their ability to communicate.

Communication disorders that affect speech, language or hearing affect one in every 10 people in the United States, according to the Academy for Educational Development. Patients with communication disorders find it difficult to use words or understand language. They may struggle in academic settings and may have problems with social interaction. In severe cases, patients may have difficulty functioning independently later in life.

Communication disorders identified by the American Psychiatric Association (APA) include:

• Expressive language disorder. Impaired ability to express oneself through language (e.g., verbal, sign language). This includes difficulty with vocabulary, production of complex sentences and recall of words. These difficulties may affect school or work performance and social relationships. The condition may result from developmental problems (which may be hereditary) or as a complication of medical conditions such as encephalitis (inflammation of the brain) or malnutrition.
  
  Most commonly, the disorder is developmental in nature, and patients show substantial improvement by late adolescence. When caused by a medical complication, the prognosis depends on the severity of the condition that triggered the disorder. Between 10 and 15 percent of children younger than age 3 have some form of expressive language disorder, according to the APA. By the time children enter school, rates drop to between 3 and 7 percent.
  
  
• Mixed receptive-expressive language disorder. Similar to expressive language disorder, but also includes an impaired ability to understand language. It can be especially difficult to detect this impairment, which is usually only revealed through formal testing. Problems understanding speech usually begin by age 4. In mild cases, patients may have difficulty understanding certain words or statements. More severe cases can cause a complete inability to understand basic vocabulary or simple sentences. This disorder appears to be less common than expressive language disorder.
  
  Although many children with mixed receptive-expressive disorder later develop normal language abilities, the prognosis is often less favorable than for children with expressive language disorder. Mixed receptive-expressive disorder due to developmental problems affects up to 5 percent of preschool children and 3 percent of school-age children, according to the APA. Acquisition of this disorder due to a medical complication is relatively uncommon.
  
  
• Phonological disorder (also known as developmental articulation disorder). Inability to use appropriate sounds while speaking, given the individual’s age, developmental stage and dialect. Some patients may experience little or no impairment of their speech, whereas others may be completely unintelligible. Misarticulated sounds tend to be those typically acquired later in development. These include the sounds “l,” “r,” “s,” “z,” “th” and “ch.” Lisping is especially common. The cause of phonological disorder is unknown, although heredity is believed to play a role.
  
  Milder forms of phonological disorder (e.g., lisping) are most common and tend to resolve by about age 6. About 2 percent of 6- and 7-year-olds have moderate to severe forms of the disorder, according to the APA. Many of these cases resolve over time, with just 0.5 percent still affected at age 17.
  
  
• Stuttering. Interruptions of a person’s ability to speak fluently and form the words and sentences necessary for verbal communication. It is normal for children between the ages of 2 and 5 years to stutter. In most cases, the condition resolves over time, often by age 16. However, some people have stuttering problems that persist or worsen as they get older. Sometimes stuttering remains a lifelong problem.
  
  According to the APA, 1 percent of children who have not yet reached puberty are affected by stuttering. This drops to just 0.8 percent in adolescence. Males are more likely to stutter than females.

Additional communication disorders include:

• Aphasia. Impaired ability to use and understand spoken and written language. Aphasia involves a loss of previously learned communication skills. Causes of aphasia include brain injury, stroke and Alzheimer’s disease.
  
  
• Auditory processing disorder. Impaired ability to recognize subtle differences in sounds and words. This disorder is not completely understood, although it is not caused by hearing problems or intellectual deficits. Also known as central auditory processing disorder, auditory perception problem, auditory comprehension deficit, central auditory dysfunction, central deafness or word deafness.
  
  
• Apraxia of speech. A speech disorder that may occur due to brain damage in adults or due to developmental problems in children. Children with apraxia often understand language spoken to them better than they can speak to others. Apraxia causes difficulty in connecting sounds and syllables to form words in the correct way. Its severity varies among patients. Apraxia of speech is also known as verbal apraxia or dyspraxia.