10 Evaluating level of Intellectual Disability

Diagnosing level of disability (mild, moderate, severe, profound)

Why is it important? Under the British Columbia (BC) Ministry of Education Special Needs Categories, the designation of Mild Intellectual Disabilities (“K”) is funded through School-based funding. It does not bring extra funding to the district, while Moderate to Profound Intellectual Disabilities (“C”) does bring extra funding to the district. The level of disability may also be relevant to the child’s classroom placement. Thus, if you think the child has a moderate or more severe disability it is essential to be explicit in the level of disability. In contrast, the level of intellectual disability is irrelevant for access to community services in British Columbia outside of the schools.

What is the challenge? Standardized IQ and adaptive functioning tests do not differentiate well between moderate, severe and profound intellectual disabilities. The DSM-5 is the go-to place to find descriptions of the levels of disability. However, outside of the Conceptual domain, level of disability is mostly described in terms of adult-attained competency. Level of disability is more difficult to evaluate in children who are still developing. Further, the level of disability may vary in an individual over time. In addition to the DSM-5, Tasse and colleagues (2019^[1]) elaborate on the DSM-5 criteria for levels of intellectual disability. They list what individuals at each level of disability can typically do “by the end of the developmental period.” Also helpful is the work of Schalock & Luckasson (2015^[2]).

Thus, while we need to be very clear about the distinction of intellectual disability versus not intellectual disability, it is OK to state “moderate to severe range” or “severe to profound range.” For those under age 5 who have multiple disabilities, a DSM-5 diagnosis of Global Developmental Delay (GDD) may be most appropriate. A formal diagnosis of GDD allows a child to access Children and Youth with Special Needs (CYSN) in BC. To continue to receive CYSN services past age 7, the child must be re-evaluated. DSM-5 also allows for “Unspecified Intellectual Disability” for “individuals over the age of 5 years when assessment of the degree of intellectual disability (intellectual developmental disorder) by means of locally available procedures is rendered difficult or impossible because of associated sensory or physical impairments, as in blindness or prelingual deafness; locomotor disability; or presence of severe problem behaviours or co-occurring mental disorder… Requires reassessment after a period of time.” If you use this category, be sure to state (if appropriate) that the individual clearly has an Intellectual Disability (& meets DSM-5 criteria) and whether you think re-assessment is necessary. Under current regulations, BC’s community services (CYSN and CLBC) will accept a diagnosis of “Unspecified Intellectual Disability.”