Developmental Delay

A developmental delay is broadly defined as any significant delay in a child's physical, cognitive, behavioral, emotional, or social development, due to one or more various reasons.

Developmental delay refers to any significant lag in a child's physical, cognitive, behavioral, emotional, or social development, as assessed by a physician, therapist, early intervention specialist, or other trained professional. The two most frequent reasons for diagnosing a child with a developmental delay involve those psychological or physiological systems with reliable, valid, and consistent norms. This is especially true for cognitive, motor, and language development. Because it is documented that most children begin to crawl by about 12 months of age and walk before the end of the second year, a child who is more than six months delayed in attaining those two milestones, depending upon other life and health circumstances, would probably be classified as developmentally delayed and the primary caregivers advised to seek early intervention or other appropriate therapies.

Most children begin to speak their first words by about 18 months of age; by three years of age most are putting two or three words together into brief sentences. A child who is not speaking words or sentences by the third birthday, barring other intervening circumstances, might be considered developmentally delayed, and, as in motor development delay, the primary caregivers would likely be advised to seek further assessment or intervention services.

Other developmental problems that children show may be caused by genetics, such as Down syndrome or any of the myriad genetic abnormalities/syndromes that have been classified; they may have possible multiple causative factors, such as those on the autism spectrum; or be medically or trauma related, such as cerebral palsy, brain injuries, hearing loss due to multiple ear infections, severe or chronic medical conditions (such as cancer or heart or kidney disease), or abuse-related delays. Some of those delays may be temporary and correctable, allowing the child to catch up to the peer group, such as speech delays related to hearing loss corrected by placement of ear tubes, or vision-related motor delays ameliorated by glasses and vision therapy. Delays related to genetics, such as those associated with Down syndrome, may be permanent.

Some delays may not be detected until the child begins to attend school. Most children, depending upon academic opportunities, are able to read single words by the second grade of elementary school. Children who cannot do so may be diagnosed with reading or other forms of learning differences, depending on the type of reading challenge present.

Physical development is typically assessed by measuring progress in both fine and gross motor skills. Potential problems are indicated by muscles that are either too limp or too tight, also called low and high tone, or hytonicity and hypertonicity. Jerky or uneven movements are another indication, as are abnormalities in reflexes (too slow, too rapid, or absent). Marked delays in motor development may indicate the presence of a neurological condition such as mild cerebral palsy. Neurological problems may also be diagnosed when a child's head circumference is excessive or increasing either too fast (sometimes called hydrocephalus, depending upon the cause) or too slowly (sometimes referred to as microcephaly). Although physical and cognitive delays may occur together, the presence of one does not necessarily indicate the presence of the other.

Important cognitive attainments that medical practitioners look for in infants during the first two years of life include object permanence, an awareness of causality, and differing reactions to strangers and familiar individuals. Cognitive delays may be due to a wide variety of causative factors, including prenatal stressors, prenatal substance exposure, prenatal toxin exposure (either absorbed from the environment or ingested by the birth mother), and a variety of different types of genetic or physiologic dysfunctions. Developmental milestones achieved and subsequently lost are a cause for concern and should be assessed and investigated, as the loss of function could be indicative of a degenerative neurological condition.

Developmental screening is a routine part of wellchecks and other physical examinations for babies and children. Parents concerned about any aspect of their child's development are generally advised to seek the opinion of a pediatrician, early intervention professional, or appropriate specialist. Numerous assessment instruments are available to use in determining developmental level and rate, depending upon the area of concern, such as language, motor, or perceptual processing.

See also Assessment, psychological ; Bayley Scales of Infant Development; Birth ; Child development .



Howlin, Patricia, et al. The SAGE Handbook of Developmental Disorders. Los Angeles: SAGE, 2011.

Levine, Laura E., and Joyce Munsch. Child Development: An Active Learning Approach. Thousand Oaks, CA: SAGE, 2011.

Miller, Patricia H. Theories of Developmental Psychology. New York: Worth, 2011.


American Academy of Family Physicians. “Screening for Developmental Delay.” (accessed September 17, 2015).

Centers for Disease Control and Prevention. “Developmental Disabilities.” (accessed September 17, 2015).

National Institutes of Health. “Genetics Home Reference.” (accessed September 17, 2015).

University of Michigan Health System. “Developmental Delay.” (accessed September 17, 2015).