Defining the Diagnosis

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Learning about developmental delay and intellectual disability will give you the tools to better understand and support your child. This knowledge will also help you build a proactive partnership with your child’s medical and educational team to build a plan of care.

Description of Developmental Delay, Intellectual Disability and Developmental Disabilities

Disclosure: While this toolkit will primarily focus on intellectual disability and developmental delay, the information and resources may also be relevant to children with other developmental disabilities. In this toolkit we will use the term Developmental Delay (DD) instead of Global Developmental Delay.

Children under the age of 5 who have delays in at least two areas of development, such as motor, language, cognition, social and adaptive functioning, are diagnosed with Global Developmental Delay (GDD). Within a year of the initial GDD diagnosis, a re-evaluation should be scheduled with a specialized physician, a psychologist, or other provider to monitor the child’s development and progress.

Children with GDD have an increased risk for a later diagnosis of Intellectual Disability (ID). ID is defined by low intellectual and adaptive skills and is diagnosed between the ages of 5 to 18. Intellectual disability, Cerebral Palsy and Autism Spectrum Disorder are part of the Developmental Disabilities group. Developmental Disabilities are disorders with ongoing physical, learning, language or behavior difficulties which start before the age of 22 and significantly impact daily functioning.

Criteria for Intellectual Disability

According to the American Psychiatric Association’s 2013 DSM-5 diagnostic criteria, the diagnosis of ID requires the following three criteria:

Low intellectual skills which are confirmed by an evaluation done by a psychologist and an IQ test score below 70-75.
Low adaptive skills that impact at least one activity of daily living such as communication, social participation and independence. The daily living activities will require support in two or more settings, such as home, school, work, and community. Adaptive skills are evaluated and scored by a clinician based on reports from caregivers and providers who are familiar with the individual’s performance.
Evidence of low intellectual and adaptive skills before the age of 18 years.

Types of Adaptive and Intellectual Skills

There are different types of intelligence, including reasoning, problem solving, planning, high-level (abstract) thinking, judgment, academic learning, and learning from experience.

Adaptive skills include daily activities which people perform by themselves and are expected within their community, culture, and age group. The three types of adaptive skills are conceptual, social, and practical.

Conceptual skills include language, reading, and writing (literacy); knowledge of money, time, and numbers (mathematics); thinking; memory; independent functioning; and judgment in new situations.
Social skills are defined by the ability to interact with other people and include communication with others, being compassionate, being able to make friends and to understand social situations. Social responsibility, self-esteem, being naive, and the ability to follow the rules and to avoid being bullied (victimized) may also be evaluated.
Practical skills consist of activities to take care of oneself such as eating, dressing, mobility and being toilet trained. Following a schedule or routine, using a telephone, managing money, preparing meals, job skills, and abilities to use transportation and travel and to maintain health care, and safety may also be evaluated.

Severity Level of Intellectual Disability

Severity is based on the scores of adaptive functioning and will determine the level of support the individual will need. IQ scores are not used to determine the severity of ID.

GENERAL INFORMATION ABOUT DEVELOPMENTAL DELAY (DD) AND INTELLECTUAL DISABILITY (ID)

Occurrence of DD and ID

ID has been reported to occur in all racial, ethnic, and socioeconomic groups. According to the American Psychiatric Associations 2013 DSM-5 diagnostic criteria, mild ID is 1.6 times more common in males and severe ID is 1.2 times more common in males.
One in six children or 17.8 % of children aged 3-17 have one or more developmental disabilities, including ID and DD. Among these children, the prevalence of ID is 1.2%. This data was reported by the CDC, based on parent surveys collected in the U.S. from 2015-2018.
Based on data analyzed from a 2017 Global Burden of Disease study, an estimated 11.2% of all children and adolescents globally had at least one of the four disabilities measured (epilepsy, intellectual disability, vision and hearing loss). Among these children and adolescents, the prevalence of intellectual disability was 3.2%.
According to a study published by Global Research on Developmental Disabilities Collaborators, it is estimated that about 53 million children under 5 years have developmental disabilities globally. The majority of these children live in low- and middle-income countries. Intellectual disability was found to be the largest contributor to years lived with disability.

Potential Impact on Development

Children with DD/ID have delays in reaching developmental milestones, such as the ability to express themselves through words and to understand spoken language. Children with DD/ID who do not develop words may connect or communicate in other ways, such as facial expression, eye contact, gestures and sign language. These children may benefit from learning to communicate through augmentative and alternative communication, which includes communication through pictures, sign language and electronic devices.
Children with DD/ID may have delays in developing fine motor skills, such as the ability to use their hands for different tasks, like holding a crayon, cutting with scissors, drawing and building with blocks.
Gross motor skills, such as walking or running, may develop later in some children with DD/ID.
Children with DD/ID may also need additional guidance in developing creative play and independence skills, like eating, toilet training, and getting dressed.

Supports for Children with ID/DD

Most individuals with ID have a mild form and are often not diagnosed until school age. During school years, children may need additional support for learning to read, use numbers or writing. With support from parents, teachers, and other providers, all children with DD/ID will continue to learn at their own pace. Providing a positive environment with encouragement and recognition of a child's progress will help maintain the child's well-being, self-esteem and confidence.
Early on caregivers and teachers need to start building independence skills in children. During school, the students receive transition planning to prepare them for life after graduation. Many of these students will be able to get training to prepare them to get a job or perform work in a supervised placement. As a result, more and more people with ID are employed today. Most individuals with ID will be able to live independently and need guidance only for complex decisions and tasks.
A large number of people with ID are athletes, with millions worldwide participating in Special Olympics. Through training and team activities Special Olympics is one of the community programs which improves independence, leadership, and social skills of individuals with ID.

Genetic and Environmental Causes

In most cases, it is unknown what causes DD/ID; however, in some cases a genetic or environmental factor can be identified. Among the known causes for ID/DD, a genetic factor is the most common. Abnormal brain formation and structure, brain tumors and metabolic conditions can also cause DD/ID. They can also be caused by a known environmental factor during pregnancy, around birth or shortly thereafter.

The most common genetic disorders that cause DD/ID include: