Developmental disability

Diagnostic criteria for intellectual disabilities (ID) have been developed by two professional organisations. Each has its own merits:

1. The American Psychiatric Association (APA), which publishes the Diagnostic and Statistical Manual of Mental Disorders (DSM-5, APA 2013);

2. The American Association on Intellectual and Developmental Disabilities (AAIDD formerly AAMR).

A summary of the diagnostic criteria in DSM-5 are helpful in identifying developmental disorders:

1. Deficits in intellectual functioning: This includes various mental abilities:

Reasoning; Problem-solving; Planning; Abstract thinking; Judgment;

 ability to learn in school via traditional teaching methods ( Academic learning);

 the ability to learn through experience, trial and error, and observation ( Experiential learning).These mental abilities are measured by an IQ test. A score of approximately two standard deviations below average represents a significant cognitive deficit. These scores would occur at about 2.5% of the population. Or stated differently, 97.5% of people of the same age and culture would score higher. The tests used to measure IQ must be standardized and culturally appropriate. This is typically an IQ score of 70 or below.

2. Deficits or impairments in adaptive functioning

This includes the skills needed to live in an independent and responsible manner. Limited abilities in these life skills make it difficult to achieve age-appropriate standards of behaviour. Without these skills, a person needs additional supports to succeed in school, work, or independent life. Deficits in adaptive functioning are measured using standardized, culturally appropriate tests.

Various skills are needed for daily living:

Communication: This refers to the ability to convey information from one person to another. Communication is conveyed through words and actions. It involves the ability to understand others, and to express one's self through words or actions.

Social skills: This refers to the ability to interact effectively with others. We usually take social skills for granted. However, these skills are critical for success in life. These skills include the ability to understand and comply with social rules, customs, and standards of public behaviour. This intricate function requires the ability to process figurative language and detect unspoken cues such as body language.

Personal independence at home or in community settings: This refers to the ability to take care of yourself. Some examples are bathing, dressing, and feeding. It also includes the ability to safely complete day-to-day tasks without guidance. Some examples are cooking, cleaning, and laundry. There are also routine activities performed in the community. This includes shopping for groceries and accessing public transportation.

School or work functioning: This refers to the ability to conform to the social standards at work or school. It includes the ability to learn new knowledge, skills, and abilities. Furthermore, people must apply this information in a practical, adaptive manner; without excessive direction or guidance.

3. These limitations occur during the developmental period. This means problems with intellectual or adaptive functioning were evident during childhood or adolescence. If these problems began after this developmental period, the correct diagnosis would be the neurocognitive disorder. For instance, a traumatic brain injury from a car accident could cause similar symptoms.


The American Psychiatric Association's (APA) diagnostic criteria for intellectual disability (ID, formerly mental retardation) are found in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5, APA 2013).



Last modified
17 August 2020

9843-4 Head Occipital-frontal circumference

3137-7 Body height Measured

Units: cm


F81.9 Developmental Disorder

Applicable to

  • Knowledge acquisition disability 
  • Learning disability 
  • Learning disorder 
Rare Condition

Autosomal dominant mental retardation-50

Autosomal dominant mental retardation-50 is associated with NAA15 gene mutations in large cohorts of DNA samples of people with mild to severe developmental delay and/or...

Autosomal dominant mental retardation-18

The name of this condition comprises GATAD2B ‘syndrome’ or GAND as well as ‘severe intellectual disability-poor language-strabismus-grimacing face-long fingers syndrome’.

The cause is a loss...

CDKL5 deficiency

CDKL5 deficiency is characterized by early-onset seizures, often presenting as infantile spasms and usually occurring within the first 3 months of life, global developmental delay...

Chromosome 21 Down syndrome

Down syndrome (DS) is the most common chromosomal abnormality. The syndrome named after L. Down, who described the associated clinical features in 1866. End of the 1950’s...

Coffin Lowry Syndrome

Coffin Lowry syndrome is a rare genetic disorder characterized by

  • mental retardation;
  • abnormalities of the head and facial (craniofacial) area;
  • large, soft hands with short...

Oculo-Auriculo-Vertebral Spectrum (Goldenhar Syndrome)

In the total spectrum of OAVS are many syndromes. One of them is Goldenhar Syndrome (GHS). Goldenhar syndrome is a rare congenital defect in the...


Phenylketonuria is an autosomal recessive inborn error of phenylalanine metabolism caused by variants in the gene encoding phenylalanine hydroxylase (PAH). PAH deficiency leads to accumulation...

Shwachman Diamond Syndrome

Shwachman-Diamond syndrome is complex condition which affects different body functions.

The pancreas  produces less enzymes for the uptake of food. 

The bone marrow malfunctions and...

Neuronal ceroïdlipofuscinose

The group of disorders known as the neuronal ceroid lipofuscinoses have common features including a variable age of onset, motor and mental decline, epilepsy, and visual...

Chromosome Ring 20 Syndrome

Chromosome Ring 20 syndrome is a rare chromosomal disorder characterized by medically hard to control epilepsy, nocturnal subtle seizures, behavioural problems and mild mental impairment...


Can be an early sign of developmental disabilities, or may be caused by short-lived issues, such as a speech delay being caused by hearing loss from...

General Medical Guideline