Speech Sound Disorder (Phonological Disorder)

Speech Sound Disorder (also known as Phonological Disorder) is a disorder where speech sound production is not consistent with what is expected based on the child's developmental stage and age. Additionally, the speech production deficits must not be due to a physical, structural, neurological, or hearing impairment. Children with the disorder may not have knowledge of phonological speech sounds, or be unable to coordinate movements (i.e. - articulation) for speech.


There is a prevalence of speech sound disorders in young children is 8 to 9 percent.[1]


Language disorder (especially in those expressive deficits) may co-occur with speech sound disorder. Individuals may also have a history of delay or poor coordination involving facial musculature (e.g. - chewing, maintaining mouth closure, and nose blowing).

What is the Timeline of Development of Speech?

In normal children, at age 2, only about 50% of speech may be understandable. By age 4, overall speech should be intelligible. By age 7, most speech sounds and words should be produced clearly and pronounced accurately. The most frequently misarticulated sounds are the “late eight” sounds (children may have difficulty with these sounds up until age 8 and this is normal). The sounds are (l, r, s, z, th, ch, dzh, and zh).
Criterion A

Persistent difficulty with speech sound production that interferes with speech intelligibility or prevents verbal communication of messages.

Criterion B

The disturbance causes limitations in effective communication that interfere with social participation, academic achievement, or occupational performance, individually or in any combination.

Criterion C

Onset of symptoms is in the early developmental period.

Criterion D

The difficulties are not attributable to congenital (i.e. - during fetal development) or acquired conditions, such as cerebral palsy, cleft palate, deafness or hearing loss, traumatic brain injury, or other medical or neurological conditions. Hereditary and genetic disorders (e.g. - Down syndrome) are excluded from this criterion.

Speech sound disorder can be due to various etiologies, and thus is a heterogeneous condition. For example, individuals with genetic disorders such as Down syndrome, DiGeorge (22q11.2 Deletion) syndrome, and the FoxP2 gene mutation may have speech sound disorder.

  • Normal variations in speech
    • Consider regional, social, or cultural/ethnic variations of speech before giving the diagnosis
  • Hearing or other sensory impairment
    • Hearing impairment or deafness may result in abnormalities of speech. Only when the language deficits are in excess of what is expected, should a diagnosis of speech sound disorder may be made.
  • Structural deficits
    • Speech impairment can be caused by structural deficits such as cleft palate.
  • Dysarthria
    • Speech impairment can be due to a motor disorder such as cerebral palsy. This is dysarthria and not speech sound disorder.
    • Limited speech might be due to selective mutism. Selective mutism may develop concurrently in children with speech disorder due to embarrassment about their impairments. Most children with selective mutism have normal speech in comfortable environments, such as at home or with friends.

Most children with speech sound disorder respond well to speech therapy. Speech difficulties often improve over time, and the disorder may not be lifelong. For some, certain speech errors can persist into adulthood.