Abstract
Conceptual Background
Disorders of Intellectual Development (DID) in the International Classification of Diseases, 11th Revision (ICD-11) are defined by the presence of significant limitations in intellectual functioning across various domains. ICD-11 adds that intellectual functioning of two or more standard deviations below the mean measured using standardised tests of intelligence will be classified as DID. This classification of DID in the latest classificatory system leaves out a significant group of individuals whose intellectual functioning is on the border between normal and intellectual disability. Described as borderline intellectual functioning (BIF), this group of people has intelligence between 1 and 2 standard deviations below the mean on the normal curve of the distribution of intelligence (roughly an IQ between 70 and 85). 1 Various estimates report that around 12%–14% of the population suffers from BIF. 2
Despite a prevailing understanding that this is a clinically meaningful group, which is often underrecognised and rarely addressed, it does not find a mention in the recent classificatory system as a disorder. Recent evidence from systematic reviews has reinforced that BIF represents a consistent pattern of cognitive and adaptive difficulties rather than merely a statistical category, with reproducible deficits across executive functioning, memory and adaptive behaviour domains.3, 4 Individuals in this population group have deficits in visual performance, short-term and long-term memory, working memory capacity, and processing speed, and have difficulties in catching up with the increasing demands in various domains as they grow older. BIF is associated with difficulties in social, academic and vocational functioning, and without appropriate supports, the likelihood of poor functional outcomes is high.
Psychiatric Comorbidity, Barriers and Service Gaps
Although not classified as a disorder in either the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) or ICD-11, people who function in the borderline range of intelligence represent a vulnerable group with specific needs. Authors in the past have highlighted that these individuals are at greater risk of experiencing physical health problems, difficulties with activities of daily living, limited social support, poverty and no access to specialised services. They also have difficulties with complex social demands and major life transitions. They are more predisposed to developing mental disorders when compared with those with either normal intelligence or mild intellectual disability. Around 40% of those with BIF have at least one comorbid psychiatric disorder, with attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder, depression, anxiety, behavioural problems and substance use being more prevalent compared to the general population. This has relevance in the diagnosis and management of these disorders. Emerging literature also highlights the problem of diagnostic overshadowing in this group, where cognitive limitations obscure co-occurring psychiatric conditions, leading to delays in identification and suboptimal treatment outcomes.4 BIF comorbid with psychiatric illness may pose challenges in diagnosis and management.
Despite the above-mentioned difficulties and various life challenges and mental health issues that these individuals face, they are largely missing from inclusion in research and policy and lack appropriate support. Additionally, mental health professionals often lack the skills required to identify those with BIF and expertise in treating psychiatric disorders in this population. It is estimated that only around 27% of children and adolescents with BIF are identified and receive help. These children and adolescents have a need for specialised educational support, a modified school syllabus and aid at school.
Policy Context and the ‘No Man’s Land’
The Rights of Persons with Disabilities (RPwD) Act, 2016, provides for the assessment and certification of disability in India. It also provides for various supports for persons with benchmark disability, which is fixed at 40% disability. This 40% threshold acts as a minimum criterion for access to specialised entitlements such as reservations in higher education, reservations in jobs, age relaxations and concessions in exams. In the latest gazette on the assessment of disability under the RPwD Act, published by the Ministry of Social Justice and Empowerment in March 2024, it is mentioned that those with borderline disability with Vineland Social Maturity Scale (VSMS) scores from 70 to 84 will be deemed to have 25% disability. 5 This effectively means that those with BIF will be deprived of any pertinent supports and resources. This creates a structural gap wherein individuals with measurable functional impairment remain ineligible for formal support systems, reinforcing their position within a service and policy ‘blind spot’. Contrary to this, authors in the past have debated that it is difficult to differentiate between BIF and mild intellectual disability, with impairment patterns being almost identical.
These arguments underscore that individuals with BIF are a particularly vulnerable group that has been neglected in mental health research and treatment frameworks, as well as insufficiently addressed in governmental policies. Consequently, they occupy a ‘no man’s land’, wherein their inherent cognitive limitations impede optimal social and academic integration, while systemic gaps in services and policy further compound their marginalisation. Kataria and Philip have argued towards unifying mild intellectual disability and BIF as one category to allow early recognition and access to necessary interventions and disability protections. 6
Implications for Research, Clinical Practice and Policy
It is imperative to expand research on the epidemiology, mental health morbidity, and specific needs and support requirements of individuals with BIF. Future research should also prioritise longitudinal and context-specific data from low- and middle-income countries to better understand educational trajectories, transition outcomes and service gaps in this population. Such evidence would be crucial in informing governmental policies and facilitating the development and integration of appropriate support systems for this population. Mental health services will also have to enhance professional training to identify and manage BIF, along with developing strategies to manage comorbid psychiatric disorders. This would reduce diagnostic overshadowing, promote timely recognition, and enable individualised and developmentally sensitive interventions. Taken together, these approaches are likely to improve the adaptive functioning, academic outcomes and vocational prospects of those with BIF.
Conclusion
In conclusion, BIF is a clinically relevant yet underrecognised and underserved entity. Despite its high prevalence, it has not attracted requisite importance in diagnostic classification, clinical practice and policy frameworks. This has contributed to delayed identification, unmet mental health needs and suboptimal outcomes. Recognising BIF as a priority area for clinical attention and policy reform is essential to ensure that this population does not continue to remain in the ‘no man’s land’ between normality and disability. In future, bolstering policy recognition and service provision for BIF will enhance long-term vocational, social and academic outcomes for this vulnerable population.