Diagnostic Requirements #

Essential (Required) Features: #

• The presence of significant limitations in intellectual functioning across various domains such as perceptual reasoning, working memory, processing speed, and verbal comprehension. There is often substantial variability in the extent to which any of these domains are affected in an individual. Whenever possible, performance should be measured using appropriately normed, standardized tests of intellectual functioning and found to be approximately 2 or more standard deviations below the mean (i.e., approximately less than the 2.3rd percentile). In situations where appropriately normed and standardized tests are not available, assessment of intellectual functioning requires greater reliance on clinical judgment based on appropriate evidence and assessment, which may include the use of behavioural indicators of intellectual functioning (see Table 6.1).
• The presence of significant limitations in adaptive behaviour, which refers to the set of conceptual, social, and practical skills that have been learned and are performed by people in their everyday lives. Conceptual skills are those that involve the application of knowledge (e.g., reading, writing, calculating, solving problems, and making decisions) and communication; social skills include managing interpersonal interactions and relationships, social responsibility, following rules and obeying laws, as well as avoiding victimization; and practical skills are involved in areas such as self-care, health and safety, occupational skills, recreation, use of money, mobility and transportation, as well as use of home appliances and technological devices. Expectations of adaptive functioning may change in response to environmental demands that change with age. Whenever possible, performance should be measured with appropriately normed, standardized tests of adaptive behaviour and the total score found to be approximately 2 or more standard deviations below the mean (i.e., approximately less than the 2.3rd percentile). In situations where appropriately normed and standardized tests are not available, assessment of adaptive behaviour functioning requires greater reliance on clinical judgment based on appropriate assessment, which may include the use of behavioural indicators of adaptive behaviour skills (see Tables 6.2 through 6.4).
• Onset occurs during the developmental period. Among adults with Disorders of Intellectual Development who come to clinical attention without a previous diagnosis, it is possible to establish developmental onset through the person’s history, i.e., retrospective diagnosis.

Severity specifiers: #

The severity of a Disorder of Intellectual Development is determined by considering both the individual’s level of intellectual ability and level of adaptive behaviour, ideally assessed using appropriately normed, individually administered standardized tests. Where appropriately normed and standardized tests are not available, assessment of intellectual functioning and adaptive behaviour requires greater reliance on clinical judgment based on appropriate evidence and assessment, which may include the use of behavioural indicators of intellectual and adaptive functioning provided in Tables 6.1 through 6.4.

Generally, the level of severity should be assigned on the basis of the level at which the majority of the individual’s intellectual ability and adaptive behaviour skills across all three domains (i.e., conceptual, social, and practical skills) fall. For example, if intellectual functioning and two of three adaptive behaviour domains are determined to be 3 to 4 standard deviations below the mean, Moderate Disorder of Intellectual Development would be the most appropriate diagnosis. However, this formulation may vary according to the nature and purpose of the assessment as well as the importance of the behaviour in question in relation to the individual’s overall functioning.

Additional Clinical Features: #

• There is no single physical feature or personality type common to all individuals with Disorders of Intellectual Development, although specific aetiological groups may have common physical characteristics.
• Disorders of Intellectual Development are associated with a high rate of co-occurring Mental, Behavioural or Neurodevelopmental Disorders. However, clinical presentations may vary depending on the individual’s age, level of severity of the Disorder of Intellectual Development, communication skills, and symptom complexity. Some disorders, such as Autism Spectrum Disorder, Depressive Disorders, Bipolar or Related Disorders, Schizophrenia, Dementia, and Attention Deficit Hyperactivity Disorder, occur more commonly than in the general population. Individuals with a co-occurring Disorder of Intellectual Development and other Mental, Behavioural, or Neurodevelopmental Disorders are at similar risk for suicide as individuals with mental disorders who do not have a co-occurring Disorder of Intellectual Development.
• Problem or challenging behaviours such as aggression, self-injurious behaviour, attention-seeking behaviour, oppositional defiant behaviour, and sexually inappropriate behaviour are more frequent among those with Disorders of Intellectual Development than in the general population.
• Many individuals with Disorders of Intellectual Development are more gullible and naïve, easier to deceive, and more prone to acquiescence and confabulation than people in the general population. This can lead to various consequences including greater likelihood of victimization, becoming involved in criminal activities, and providing inaccurate statements to law enforcement.
• Significant life changes and traumatic experiences can be particularly difficult for a person with Disorders of Intellectual Development. Whereas the timing and type of life transitions vary across societies, it is generally the case that individuals with Disorders of Intellectual Development need additional support adapting to changes in routine, structure, or educational or living arrangements.
• There are many medical conditions that can cause Disorders of Intellectual Development and that are, in turn, associated with specific additional medical problems. A variety of prenatal (e.g., exposure to toxic substances or harmful medications), perinatal (e.g., labour and delivery problems), and postnatal (e.g., infectious encephalopathies) factors may contribute to the development of Disorders of Intellectual Development, and multiple aetiologies may interact. Early diagnosis of the aetiology of a Disorder of Intellectual Development, when possible, can assist in the prevention and management of related medical problems (e.g., frequent thyroid disease screening is recommended for individuals with Down Syndrome). If the aetiology of a Disorder of Intellectual Development in a particular individual has been established, the diagnosis corresponding to that aetiology should also be assigned.
• Individuals with Disorders of Intellectual Development are at greater risk for a variety of health (e.g., epilepsy) and social (e.g., poverty) problems across the lifespan.

Boundary with Normality (Threshold): #

• In Disorders of Intellectual Development, a measure of intelligence quotient (IQ) is not an isolated diagnostic requirement to distinguish disorder from normality, but should be considered a proxy measure of the ‘significant limitations in intellectual functioning’ that partially characterize Disorders of Intellectual Development. IQ scores may vary as a result of the technical properties of the specific test being used, the testing conditions, and a variety of other variables and also can vary substantially over the individual’s development and life course. The diagnosis of Disorders of Intellectual Development should not be made solely based on IQ scores but must also include a comprehensive evaluation of adaptive behaviour.
• Scores on individually administered standardized tests of intellectual and adaptive functioning may vary considerably over the course of an individual’s development, and it is quite possible that during the developmental period, a child may meet the diagnostic requirements of Disorders of Intellectual Development on one occasion but not another. Multiple testing on different occasions during the developmental trajectory is necessary to establish a reliable estimate of functioning.
• Special care should be taken in differentiating Disorders of Intellectual Development from normality when evaluating persons with communication, sensory, or motor impairments as well as those exhibiting behavioural disturbances; immigrants; persons with low literacy levels; persons with mental disorders; persons undergoing health treatments (e.g., pharmacotherapy); and persons who have experienced severe social or sensory deprivation. If not adequately addressed during the evaluation, these factors may reduce the validity of scores obtained on standardized or behavioural measures of intellectual and adaptive functioning. For example, the reliable use of standardized measures of intellectual functioning and adaptive behaviour may pose particular challenges among individuals with motor coordination and communication impairments, and assessments must be selected that are appropriate to the individual’s capacities.
• What is sometimes termed ‘Borderline Intellectual Functioning’, defined as intellectual functioning between approximately 1 and 2 standard deviations below the mean, is not a diagnosable disorder. Nonetheless, such individuals may present many needs for supports and interventions that are similar to those of persons with Disorders of Intellectual Development.

Course Features: #

• Disorders of Intellectual Development are lifespan conditions that typically manifest during early childhood and require consideration of developmental phases and life transitions whereby periods of relatively greater need may alternate with those where less support may be necessary.
• Disorders of Intellectual Development may show individual as well as aetiology-specific variation in developmental trajectories (i.e., periods of relative decline or amelioration in functioning). Intellectual functioning and adaptive behaviour can vary substantially across the lifespan. Results from a single assessment, particularly those obtained during early childhood, may be of limited predictive use as later functioning will be influenced by the level and type of interventions and supports provided.
• People with Disorders of Intellectual Development typically need exceptional supports throughout the life span, although the types and intensities of required supports often changes over time depending on age, development, environmental factors, and life circumstances. Most people with Disorders of Intellectual Development continue to acquire skills and competencies over time. Providing interventions and supports—including education—assists with this process and, if provided during the developmental period, may result in lower support needs in adulthood.

Developmental Presentations: #

• There is wide variability in the developmental presentation and developmental trajectories of individuals with Disorders of Intellectual Development. Tables 6.2 through 6.4 provide clinicians with some of the key areas of strengths and weaknesses typically observed at different time points across development (i.e., early childhood, childhood, adolescence, and adulthood) in individuals with Disorders of Intellectual Development.
• Conditions related to Disorders of Intellectual Development may be suspected during the first days and months of life due to the presence of certain physical signs such as facial dimorphisms, congenital malformation, micro- or macrocephalia, low weight, hypotonia, physical growth retardation, metabolic problems and failure to thrive, among others.
• In older children, Disorders of Intellectual Development may manifest as problems in acquiring academic knowledge and abilities such as reading, writing, arithmetic, etc. Many children with Mild Disorder of Intellectual Development may not be referred for evaluation until school aged. Some individuals may remain undiagnosed until much later, during adolescence or adulthood.
• The manifestations of Disorders of Intellectual Development during late adolescence and the first years of adulthood may be strongly influenced by the presence of challenges related to assuming adult roles, such as postsecondary education, employment, independent living, and adult relationships.
• Older adults with Disorders of Intellectual Development may present with a more rapid onset of Dementia or declining skills than older adults in the general population. They also have significantly more difficulty gaining access to necessary supports and appropriate health care for medical problems.

Culture-Related Features: #

• The cultural appropriateness of tests and norms used to assess intellectual and adaptive functioning should be considered for each individual. Test performance may be affected by cultural biases (e.g., reference in test items to terminology or objects not common to a culture) and limitations of translation.
• In evaluating adaptive functioning, i.e., the individual’s conceptual, social, and practical skills, the expectations of the individual’s culture and social environment should be considered.
• Language proficiency must also be considered when interpreting test results, both in terms of whether the individual understood the instructions as well as its impact on verbal performance.

Sex- and/or Gender-Related Features: #

• The overall prevalence of Disorders of Intellectual Development is slightly higher in males. The prevalence of some aetiologies of Disorders of Intellectual Development differs between males and females (e.g., X-linked genetic conditions such as Fragile X Syndrome are predominantly diagnosed in males whereas Turner Syndrome occurs exclusively in females).
• A number of associated features of Disorders of Intellectual Development differ between males and females, for example in the expression of problem behaviours and co-occurring Mental, Behavioural, or Neurodevelopmental Disorders. Males are more likely to exhibit hyperactivity and conduct disturbances whereas females are more likely to exhibit mood and anxiety symptoms.
• Reduced social value and expectations placed on females as compared to males in some societies may negatively affect the accurate identification and provision of supports for females with Disorders of Intellectual Development.

Boundaries with Other Disorders and Conditions (Differential Diagnosis): #

• Boundary with Developmental Speech and Language Disorders: In Developmental Speech and Language Disorders, individuals exhibit difficulties in understanding or producing speech and language or in using language in context for the purposes of communication that is markedly below what would be expected given the individual’s age and level of intellectual functioning. If speech and language abilities are significantly below what would be expected based on intellectual and adaptive behaviour functioning in an individual with a Disorder of Intellectual Development, an additional diagnosis of Developmental Speech and Language Disorder may be assigned.
• Boundary with Autism Spectrum Disorder: Autism Spectrum Disorder is characterized by persistent deficits in reciprocal social interaction and social communication, and by a range of restricted, repetitive, inflexible patterns of behaviour and interests. Although many individuals with Autism Spectrum Disorder present with the significant limitations in intellectual functioning and adaptive behaviour observed in Disorders of Intellectual Development, Autism Spectrum Disorder can also present without general limitations in intellectual functioning. In cases of Autism Spectrum Disorder where there are significant limitations in intellectual functioning and adaptive behaviour (i.e., 2 or more standard deviations below the mean or approximately less than the 2.3rd percentile) both the diagnosis of Autism Spectrum Disorder using the ‘with Disorder of Intellectual Development’ specifier and the diagnosis of a Disorder of Intellectual Development at the corresponding level of severity should be assigned. The diagnosis of Autism Spectrum Disorder in individuals with Severe and Profound Disorders of Intellectual Development is particularly difficult, and requires in-depth and longitudinal assessments. Because Autism Spectrum Disorder inherently involves social deficits, assessment of adaptive behaviour as a part of the diagnosis of a co-occurring Disorder of Intellectual Development should place greater emphasis on the conceptual and practical domains of adaptive functioning than on social skills.
• Boundary with Developmental Learning Disorders: Developmental Learning Disorders are characterized by significant and persistent difficulties in learning academic skills including reading, writing and arithmetic, with performance in these areas markedly below what would be expected for chronological age or intellectual level. Individuals with Disorders of Intellectual Development often present with limitations in academic achievement by virtue of significant generalized deficits in intellectual functioning. It is therefore difficult to establish the co-occurring presence of a Developmental Learning Disorder in individuals with a Disorder of Intellectual Development. However, Developmental Learning Disorders can co-occur in some individuals with Disorders of Intellectual Development if, despite adequate opportunities, acquisition of learning is significantly below what is expected based on established intellectual functioning. In such cases, both disorders may be diagnosed.
• Boundary with Developmental Motor Coordination Disorder: In Developmental Motor Coordination Disorder, individuals exhibit significant delays during the developmental period in the acquisition of gross and fine motor skills and impairment in the execution of coordinated motor skills that manifest in clumsiness, slowness, or inaccuracy of motor performance. Individuals with Disorders of Intellectual Development may also display such motor coordination difficulties that impact adaptive behaviour functioning. In contrast to those with Developmental Motor Coordination Disorder, individuals with Disorders of Intellectual Development have accompanying significant limitations in intellectual functioning. However, if coordinated motor skills are significantly below what would be expected based on level of intellectual functioning and adaptive behaviour and represent a separate focus of clinical attention, both diagnoses may be assigned.
• Boundary with Attention Deficit Hyperactivity Disorder: In Attention Deficit Hyperactivity Disorder, individuals show a persistent and generalized pattern of inattention and/or hyperactivity-impulsivity that emerges during the developmental period. If all diagnostic requirements for a Disorder of Intellectual Development are met and inattention and/or hyperactivity-impulsivity are found to be outside normal expected limits based on age and level of intellectual functioning with significant interference in academic, occupational, or social functioning, both diagnoses of Attention Deficit Hyperactivity Disorder and a Disorder of Intellectual Development may be assigned.
• Boundary with Dementia: In Dementia, affected individuals, usually older adults, exhibit a decline from a previous level of functioning in multiple cognitive domains that significantly interferes with performance of activities of daily living. Both disorders can co-occur, and some adults with Disorders of Intellectual Development are at greater and earlier risk of developing Dementia. For example, individuals with Down Syndrome who exhibit a marked decline in adaptive behaviour functioning should be evaluated for the emergence of Dementia. In cases in which the diagnostic requirements for both a Disorder of Intellectual Development and Dementia are met, both diagnoses may be assigned.
• Boundary with other Mental and Behavioural Disorders: Other Mental and Behavioural Disorders such as Schizophrenia or Other Primary Psychotic Disorders may include symptoms that interfere with intellectual functioning and adaptive behaviour. A Disorder of Intellectual Development should not be diagnosed if the limitations are better accounted for by another Mental and Behavioural Disorder. However, other Mental and Behavioural Disorders are at least as prevalent in individuals with Disorders of Intellectual Development as in the general population, and co-occurring diagnoses should be assigned if warranted. In evaluating Mental and Behavioural Disorders in individuals with Disorders of Intellectual Development, signs and symptoms must be assessed using methods that are appropriate to the individual’s level of development and intellectual functioning, and may require a greater reliance on observable signs and the reports of others who are familiar with the individual.
• Boundary with sensory impairments: If not addressed, sensory impairments (e.g., visual, auditory) can interfere with opportunities for learning, resulting in apparent limitations in intellectual functioning or adaptive behaviour. If the observed limitations are solely attributable to a sensory impairment, a Disorder of Intellectual Development should not be assigned. However, prolonged sensory impairment throughout the critical period of development may result in the persistence of limitations in intellectual functioning or adaptive behaviour, despite later intervention, and an additional diagnosis of a Disorder of Intellectual Development may be warranted in such cases.
• Boundary with effects of psychosocial deprivation: Extreme psychosocial deprivation in early childhood can produce severe and selective impairments in specific mental functions such as language, social interaction, and emotional expression. Depending on the onset, level of severity and duration of the deprivation, functioning in these areas may improve substantially after the child is moved to a more positive environment. However, some deficits may persist even after a sustained period in an environment that provides adequate stimulation for development, and a diagnosis of a Disorder of Intellectual Development may be appropriate in such cases if all diagnostic requirements are met.
• Boundary with neurodegenerative diseases: Neurodegenerative diseases can be associated with Disorders of Intellectual Development but only if they have their onset in the developmental period (e.g., mucolipidosis I, Gaucher’s disease type III). If a neurodegenerative disease co-occurs with a Disorder of Intellectual Development, both diagnoses should be assigned.
• Boundary with Secondary Neurodevelopmental Syndrome: If the diagnostic requirements of a Disorder of Intellectual Development are met and the symptoms are attributed to medical conditions with onset during the prenatal or developmental period, both Disorder of Intellectual Development and the underlying medical conditions should be diagnosed. If the diagnostic requirements of a Disorder of Intellectual Development are not met (e.g., limitations in intellectual functioning without limitations in adaptive functioning) and the symptoms are attributed to medical conditions with onset during the prenatal or developmental period, a diagnosis of Secondary Neurodevelopmental Syndrome should be assigned, together with the diagnosis corresponding to the underlying medical condition.

6A00.0 Mild Disorder of Intellectual Development智力发育障碍，轻度 #

• In Mild Disorder of Intellectual Development, intellectual functioning and adaptive behaviour are found to be approximately 2 to 3 standard deviations below the mean (approximately 0.1 – 2.3 percentile), based on appropriately normed, individually administered standardized tests. Where standardized tests are not available, assessment of intellectual functioning and adaptive behaviour requires greater reliance on clinical judgment, which may include the use of behavioural indicators provided in Tables 6.1 through 6.4. Persons with a Mild Disorder of Intellectual Development often exhibit difficulties in the acquisition and comprehension of complex language concepts and academic skills. Most master basic self-care, domestic, and practical activities. Affected persons can generally achieve relatively independent living and employment as adults but may require appropriate support.轻度智力发育障碍是一种起源于发育期的疾病，其特征是智力功能和适应性行为明显低于平均水平，根据适当的规范化、单独管理的标准化测试，或在没有标准化测试的情况下，根据可比的行为指标，低于平均水平约2至3个标准差。受影响的人往往在获得和理解复杂的语言概念和学术技能方面表现出困难。大多数人掌握基本的自理、家务和实践活动。受轻度智力发育障碍影响的人在成年后一般可以实现相对独立的生活和就业，但可能需要适当的支持。

6A00.1 Moderate Disorder of Intellectual Development智力发育障碍，中度 #

• In Moderate Disorder of Intellectual Development, intellectual functioning and adaptive behaviour are found to be approximately 3 to 4 standard deviations below the mean (approximately 0.003 – 0.1 percentile), based on appropriately normed, individually administered standardized tests. Where standardized tests are not available, assessment of intellectual functioning and adaptive behaviour requires greater reliance on clinical judgment, which may include the use of behavioural indicators provided in Tables 6.1 through 6.4. Language and capacity for acquisition of academic skills of persons affected by a Moderate Disorder of Intellectual Development vary but are generally limited to basic skills. Some may master basic self-care, domestic, and practical activities. Most affected persons require considerable and consistent support in order to achieve independent living and employment as adults.中度智力发育障碍是一种起源于发育期的疾病，其特征是智力功能和适应行为显著低于平均水平，当标准化测试不可用时，根据适当的规范化、单独管理的标准化测试，或通过可比较的行为指标，大约低于平均水平3至4个标准差（大约0.003-0.1百分位）。受中度智力发育障碍影响的人的语言和学术技能习得能力各不相同，但一般仅限于基本技能。有些人可能掌握基本的自理、家务和实践活动。大多数受影响的人需要大量和持续的支持，以便在成年后实现独立生活和就业。

6A00.2 Severe Disorder of Intellectual Development智力发育障碍，重度 #

• In Severe Disorder of Intellectual Development, intellectual functioning and adaptive behaviour are found to be approximately 4 or more standard deviations below the mean (less than approximately the 0.003rd percentile), based on appropriately normed, individually administered standardized tests. Where standardized tests are not available, assessment of intellectual functioning and adaptive behaviour requires greater reliance on clinical judgment, which may include the use of behavioural indicators provided in Tables 6.1 through 6.4. Persons affected by a Severe Disorder of Intellectual Development exhibit very limited language and capacity for acquisition of academic skills. They may also have motor impairments and typically require daily support in a supervised environment for adequate care, but may acquire basic self-care skills with intensive training. Severe and Profound Disorders of Intellectual Development are differentiated exclusively on the basis of adaptive behaviour differences because existing standardized tests of intelligence cannot reliably or validly distinguish among individuals with intellectual functioning below the 0.003rd percentile.重度智力发育障碍是指起源于发育期的一种状况，其特征是智力功能和适应性行为明显低于平均水平，根据适当的规范化、单独管理的标准化测试，或当标准化测试不可用时，通过可比较的行为指标，低于平均水平约四个或更多的标准差（低于约0.003百分位数）。受影响者的语言和学习能力非常有限。他们还可能有运动障碍，通常需要在有监督的环境中获得日常支持以获得充分的照顾，但也可能通过强化训练获得基本的自理技能。由于现有的标准化智力测试不能可靠或有效地区分智力功能低于0.0030%的个体，所以严重和深度智力发展障碍只能根据适应性行为差异来区分。

6A00.3 Profound Disorder of Intellectual Development智力发育障碍，极重度 #

• In Profound Disorder of Intellectual Development, intellectual functioning and adaptive behaviour are found to be approximately 4 or more standard deviations below the mean (approximately less than the 0.003rd percentile), based on individually administered appropriately normed, standardized tests. Where standardized tests are not available, assessment of intellectual functioning and adaptive behaviour requires greater reliance on clinical judgment, which may include the use of behavioural indicators provided in Tables 6.1 through 6.4. Persons affected by a Profound Disorder of Intellectual Development possess very limited communication abilities and capacity for acquisition of academic skills is restricted to basic concrete skills. They may also have co-occurring motor and sensory impairments and typically require daily support in a supervised environment for adequate care. Severe and Profound Disorders of Intellectual Development are differentiated exclusively on the basis of adaptive behaviour differences because existing standardized tests of intelligence cannot reliably or validly distinguish among individuals with intellectual functioning below the 0.003rd percentile.智力发育极度障碍是指起源于发育期的一种状况，其特征是智力功能和适应行为明显低于平均水平，大约比平均水平低四个或更多的标准差（大约低于0.003百分点），基于单独进行的适当规范的标准化测试或在标准化测试不可用时通过可比的行为指标。受影响者的沟通能力非常有限，获得学术技能的能力仅限于基本的具体技能。他们还可能同时存在运动和感觉障碍，通常需要在有监督的环境中获得日常支持以获得充分的照顾。由于现有的标准化智力测试不能可靠或有效地区分智力功能低于0.003%的个体，因此，重度和极度智力发展障碍只能根据适应性行为差异来区分。

6A00.4 Disorder of Intellectual Development, Provisional智力发育障碍，暂定 #

• Disorder of Intellectual Development, Provisional is assigned when there is evidence of a Disorder of Intellectual Development but the individual is an infant or child under the age of four, making it difficult to ascertain whether the observed impairments represent a transient delay. Disorder of Intellectual Development, Provisional in this context is sometimes referred to as Global Developmental Delay. The diagnosis can also be assigned in individuals 4 years of age of older when evidence is suggestive of a Disorder of Intellectual Development but it is not possible to conduct a valid assessment of intellectual functioning and adaptive behaviour because of sensory or physical impairments (e.g., blindness, pre-lingual deafness), motor or communication impairments, severe problem behaviours, or symptoms of another Mental, Behavioural, or Neurodevelopmental Disorder that interfere with assessment.如果有证据表明存在智力发育障碍，但当事人是四岁以下的婴儿或儿童，不可能对智力功能和适应行为进行有效评估，或者由于感官或身体障碍（如失明、语前聋）、运动或交流障碍、严重的问题行为或同时存在的精神和行为障碍，则可指定为临时性智力发育障碍。

6A00.Z Disorders of Intellectual Development, Unspecified未特指的智力发育障碍 #

TABLE 6.1: BEHAVIOURAL INDICATORS OF INTELLECTUAL FUNCTIONING

Note: The presence or absence of particular behavioural indicators listed in the chart below is not sufficient to assign or defer a diagnosis of Disorder of Intellectual Development. Clinical judgment is a necessary component in determining whether an individual has a Disorder of Intellectual Development, and diagnosis relies on the following key assumptions being met: (1) Limitations in present functioning have been considered within the context of community environments typical of the individual’s age peers and culture; (2) Valid assessment considered cultural and linguistic diversity as well as differences in communication, sensory, motor and behavioural factors; (3) Within an individual, limitations are recognized to often coexist alongside strengths and both were considered during the assessment; (4) Limitations are described, in part, to develop a profile of needed supports; and (5) It is recognized that with appropriate supports over a sustained period, the life functioning of the affected person generally will improve (AAIDD, 2010, p. 1). Please consult the Clinical Descriptions and Diagnostic Requirements for Disorders of Intellectual Development and if applicable, Autism Spectrum Disorder, for guidance on how to determine the severity level.*

TABLE 6.2: BEHAVIOURAL INDICATORS OF ADAPTIVE BEHAVIOUR
EARLY CHILDHOOD (up to 6 years of age)

The behavioural indicators below are intended to be used by the clinician in determining the level of severity of the Disorder of Intellectual Development either as a complement to or when properly normed, standardized tests are unavailable or inappropriate given the individual’s cultural and linguistic background. Use of these indicators is predicated on the clinician’s knowledge of and experience with typically developing individuals of comparable age. Unless explicitly stated, the behavioural indicators of intellectual functioning and adaptive behaviour functioning for each severity level are what are typically expected to be mastered by the individual by 6 years of age. Please consult the Clinical Descriptions and Diagnostic Requirements for Disorders of Intellectual Development and if applicable, Autism Spectrum Disorder, for guidance on how to determine the severity level.

TABLE 6.3: BEHAVIOURAL INDICATORS OF ADAPTIVE BEHAVIOUR
CHILDHOOD AND ADOLESCENCE (6 to 18 years of age)

The behavioural indicators below are intended to be used by the clinician in determining the level of severity of the Disorder of Intellectual Development either as a complement to or when properly normed, standardized tests are unavailable or inappropriate given the individual’s cultural and linguistic background. Use of these indicators is predicated on the clinician’s knowledge of and experience with typically developing individuals of comparable age. Unless explicitly stated, the behavioural indicators of intellectual functioning and adaptive behaviour functioning for each severity level are what are typically expected to be mastered by the individual by 18 years of age. Please consult the Clinical Descriptions and Diagnostic Requirements for Disorders of Intellectual Development and if applicable, Autism Spectrum Disorder, for guidance on how to determine the severity level.

TABLE 6.4: BEHAVIOURAL INDICATORS OF ADAPTIVE BEHAVIOUR
ADULTHOOD (18+ year of age)

The behavioural indicators below are intended to be used by the clinician in determining the level of severity of the Disorder of Intellectual Development either as a complement to or when properly normed, standardized tests are unavailable or inappropriate given the individual’s cultural and linguistic background. Use of these indicators is predicated on the clinician’s knowledge of and experience with typically developing individuals of comparable age. The behavioural indicators of intellectual functioning and adaptive behaviour functioning for each severity level are what are typically expected to be mastered by the individual as an adult. Please consult the Clinical Descriptions and Diagnostic Requirements for Disorders of Intellectual Development and if applicable, Autism Spectrum Disorder, for guidance on how to determine the severity level.